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1.
adj meaning cool awesome the best
That was the sickest party ever yo.
by YO October 19, 2003
 
2.
Superlative meaning the best ever. Often used in tandem with "ever," as in "sickest ever."

Idiomatic expression or interjection indicating greatness, or any supremely positive expression. Used without another word.
During an extremely psychedelic jam session by a hippie band, various members of the audience might yell, "Sickest!" After the show they will call their friends who didn't make it to the concert to tell them they missed "the sickest ever set tonight, dude!"
by JoeSoHeady April 27, 2006
 
3.
You are out of control,wild,crazy,dumb
goin outside undecent....Yu da sickest for dat....anything funny,crazy or unordinary..deserves to be called da sickest...you's a sick nigga
by Lil-Darnell August 21, 2008
 
4.
gay,fag,dusch bag, kid that u cant stand because he so fuckin annoying.
your just the fuckin sickest kid.
by whatcolorwhat October 07, 2008