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With the stock market in nearly nonstop rally mode over the past six years, investors haven't needed to look far to uncover an abundance of growth stocks. But not all growth stocks are created equal: While some could still deliver extraordinary gains, others appear considerably overvalued, and might instead burden investors with hefty losses.

What exactly is a growth stock? Though it's arbitrary, I'll define a growth stock as any company forecast to grow profits by 10% or more annually during the next five years. To decide what's "cheap," I'll use the PEG ratio, which compares a company's price-to-earnings ratio to its future growth rate. Any figure around or below one could signal a cheap stock.

Here are three companies that fit the bill.

Plains GP Holdings LP

We'll begin the week by taking a closer look at Plains GP Holdings (NASDAQ:PAGP), a master-limited partnership that operates midstream energy infrastructure assets for crude, natural gas, and natural gas liquids.

The reason shares of Plains GP Holdings are so cheap can be tied to two factors. First, crude oil prices have fallen substantially over the past two years, reducing the desire to boost production. Without a steady increase in production, midstream operators could struggle to sign new transport, storage, and terminaling contracts.

More recently, in July Plains GP Holdings announced that it would be reducing its quarterly distribution by 11% to $0.2065 per share from its current rate. Shareholders typically don't like dividend cuts, and the expectation of a payout cut, along with steep debt levels, have weighed on Plains GP's shares.

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However, Plains GP's decision to cut its distribution is actually a smart one with a debt-to-EBITDA north of six. Having to pay less to shareholders should allow Plains GP the opportunity to either reduce existing debt levels or expand its infrastructure. With energy prices expected to rise slowly with demand, expanding infrastructure could be a surefire way to increase annual cash flow.

Additionally, the same day Plains All American Pipeline (NASDAQ:PAA) and Plains GP Holdings announced that they were cutting their distributions, Plains All American's incentive distribution rights were permanently eliminated in exchange for 245.5 million newly issued shares of Plains All American and the assumption of $593 million in outstanding debt for a subsidiary of Plains GP Holdings. In easier-to-understand terms, the removal of these incentive distribution rights makes it far easier and cheaper for Plains GP Holdings to issue common stock in order to raise capital, which could allow for quicker pipeline expansion opportunities.

Assuming management remains mindful of its spending, and energy prices continue to trend modestly higher in the years to come, Plains GP Holdings' PEG of 0.4 and dividend yield of 6% make it quite the attractive growth stock.

Vista Outdoor Inc.

Another cheap growth stock that could pique investors' interests is Vista Outdoor (NYSE:VSTO), a midcap company that develops ammunition for hunting, sport, and law enforcement, as well as hunting, sport, and firearm accessories.

The primary reason Vista Outdoor shares are cheaper now than they were three months ago can be traced to the release of its fiscal first-quarter results. Although Vista Outdoor stood by its full-year forecast, adjusted EPS for Q1 2017 came in at $0.48 compared to $0.53 in the year-ago period. Comparatively, Wall Street was expecting $0.69 in EPS in Q1 2017. This miss has erased about a quarter of Vista Outdoor's valuation since August.

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However, this quarterly miss, which the company blamed on a near-universal softness in retail sales across the country, could be the perfect buying opportunity.

One of the ironic trends that Vista Outdoor is benefiting from is the potential for Capitol Hill to pass tougher gun control laws. Following a number of unfortunate shooting incidents in the United States, some lawmakers have called for stricter regulation of access to guns, which could eventually slow gun sales and hurt ancillary sales for a company like Vista Outdoor. But Vista Outdoor has witnessed a sales increase -- consumers are loading up on fireams, ammunition, and accessories just in case a tougher gun control law is passed. Mind you, Vista Outdoor primarily sells its products for sport and not defense, but it's gone along for the ride nonetheless. Though this trend can't persist forever, it does have some near-term staying power.

Over the longer-term, Vista Outdoor is more likely to rely on M&A activity to help drive growth. Vista Outdoor has been an active shopper recently, with the company announcing the acquisition of personal hydration business Camelbak for $412.5 million last summer, completing its BRG Action Sports buyout for $400 million in April to give the company a bigger share of the cycling market, and announcing the $74 million acquisition of outdoor cooking solutions company Camp Chef in September. M&A activity could very well keep Vista Outdoor on a high-single-digit/low-double-digit sales growth trajectory in the near-term.

Sporting a PEG of 0.6, Vista Outdoor could be worth a closer inspection.

Integrated Device Technology Inc.

Last but not least, system-level solutions developer Integrated Device Technology (NASDAQ:IDTI) is a name growth investors may not want to forget.

Over the past week, Integrated Device Technology, which is more commonly referred to by its shorthand, IDT, has been walloped by the shortcomings of the Samsung Galaxy Note 7. Fires attributed to the battery have weighed on all Samsung suppliers, of which IDT is one. But IDT is much more than just a Samsung supplier, making this swoon in its share price a potentially intriguing buying opportunity.

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IDT has its hands in a number of interesting fields, including communications, computing, and automotive. The company primarily provides system solutions for 4G networks and network communications, cloud data centers, and mobile devices. Practically all of these segments are slated for phenomenal long-term growth. Telecom networking infrastructure requires constant investment, while data center growth could average nearly 11% per year between 2016 and 2020 according to a new report from Technavio. IDT also has ties with Apple, supplying the wireless charging chip for the Apple Watch.

An even bigger growth trend could be the Internet of Things, or IoT. In layman's terms, IoT describes solutions that allow systems to interact with their surroundings. Imagine thermostats that can adjust themselves or cars that can recognize when a lane change is unsafe. IDT is one of the companies involved in IoT solutions in the automotive industry with its sensor signal conditioners.

During the first quarter of fiscal 2017, IDT reported strong sales growth of 19% from all aspects of its solutions. Samsung Galaxy Note 7 aside, mobile continues to be a major driver for IDT in the near-term, while automotive could be a (pun intended) larger growth driver by the end of the decade. With a PEG ratio of one, shares of Integrated Device Technology may very well still be cheap.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.