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An urban dictionary cracka is the type of cracka that is to scared to voice his/her opinions about black/latino/whatever is not white races to their faces, but feels more comfortable posting them up on urbandictionary.com. The urban dictionary cracka frolicks online, but outside of its natural habitat (the real world) it is frequently beaten and socially shunned.

Urban dictionary crackas are most known for having hate or prejudice for an entire race because of one or two minor incidents between a person of that race.
At School-
Urban dictionary cracka: NIGGER NIGGER NIGGER
*Urban dictionary cracka gets his ass beat*

On the net-

Urban dictionary cracka: SPIC SPIC SPIC SPIC
*Urban dictionary frolicks about*
by That Real Negro January 19, 2005