Last week, Nuance Communications (NASDAQ:NUAN) adopted a "poison pill," aimed at diluting the voting powers of any shareholder who acquires more than 20% of the company's shares outstanding.

Although the company claims the measure wasn't directed at any individual shareholder or company, the move is certainly a little suspicious, considering activist investor Carl Icahn recently built his position in Nuance to more than 16% of shares outstanding.

In the following video, Fool contributor Steve Heller gives two possible reasons for why Nuance "activated" this poison pill provision. Whatever the reason may be, it's become clear that the company is on the defensive.