A yip is a short, high-pitched bark. Any dog may yip, but yips are most associated with small dogs, particularly lap dogs and puppies. Larger dogs usually only yip as an exclamation of pain or surprise.
The meanings of the word 'yip' may best be distinguished through the meanings of the closely associated words 'yelp' (a doggish exclamation) and 'yap' (a small, usually annoying and persistent bark).
While the origins of the word yip are cloudy, it most likely evolved from the Middle English yippe, meaning a cheeping sound, and used to refer to birds, not dogs.
In the game of golf, 'the yips' refer to the state of being shaky or nervous when making a shot. Therefore, 'to yip' is to flub a shot due to the yips. (Woldgolf.com actually defines it as "to mishit a putt", but I'm assuming that this is a tpyo.)