Anticipation: It's when the viewer is expecting a character to do something, or when something is expected to happen. (It's gives a bit of suspense) Again it makes an action look more realistic.
It could be a character jumping for instead or even a character about to pick something up.
Here is some anticipation in our group project.
If you look very carefully at the clown fish you will see it staring at the stickfa while falling and you expect something to happen as it stares at the stickfa, it will also start following it...the anticipation was used here to prepare the viewers for the unexpected, they surely didn't expect the stickfa to kick the fish but they expected something to happen...Anticipation could be used to make an action look more realistic...like a tennis player about to hit a tennis ball.
http://www.youtube.com/watch?v=P5_Y6dL9PtE This is the link to my video reference for anticipation, a 2D animatio where you see tennis players about to hit a tennis ball.
Here is a sample 4rm the video link above: