A small part of something, a fraction of an object.
Hey friend, perhaps I can talk you into letting me have a ch-sis of that sandwich.
*Your friend is eating some whoppers*
"Lemme get a ch-sis, comrade."
To engage in defecation. To toss a few turd stones into the old crapper.
Frank: "Christ Man! I'm feelin' it, I'm outta here man, gotta chunk a skippy!"
Jim: "Fuck thats sick!"