In the course of a competitivesituation putting down your opponent verbally or saying how good you think you are. Oftenly involving talk of moms or sisters.
Examples of Trash Talk
"You couldn't tackle me in a phone booth"
"You better stay out of the paint or I'll block you so hard I'll make your momma hurt more than I made your sister hurt last night"
"I'm so fast you couldn't see me with a telescope"