Student: I'm too selfish to think about other people, so I don't have time to be mean to him.

From my Physics class:

Talking about projectiles:
Teacher: It's like, thrown up.
Student: Throw-up?

Teacher: Which angle do we usually measure?
Student: Hypotenuse!
(later)
Teacher: I'm going to make this arrow right here (draws arrow along the y-axis from the angle to the x-axis) and you know what we're going to call it?
Same Student: Hypotenuse!

Someone, please send something in, I can't be the only person to overhear funny stuff!