Bullshit surfer lingo for "yeah" as in "chyeah" or "chyeah right." Commonly associated with football jocks, gelled hair, Hurley/Abercrombie bullshit, and other dick-tit fag-nasty bullshit people do to be fuckin' cha'.
Phonetically, it is performed in such a way:
1) press the teeth together
2) Let out a "ch-" foundation
3) Hold the "ahhhhh" note for a long period of time with your mouth open, appearing as oblivious and ignorant as possible, with volume such that it attracts the attention of females, which may lead to "getting hot puss."
Cha' as an adjective.
Cha clothing (Hurley, AE, A&F, Pac-Sun)
Cha'ster (One who is cha)
Chamillionaire (a bad singer)
"Dude, you didn't like, do the full 10 bench reps on that did you?"
"Cha', I did"
(they start blowing one another)