One who is both a slacker and a fucker. One who does absolutely nothing all day, yet still manages to fuck that up.
Cool Guy: Hey man, did you go get that case of beer for the party while i was at class today?

SlackFuck: Nawwww, i got super fucking high today though....sweet huh? Oh yeah i made you a muffaletta though...

Cool Guy: Dude, you're a total slackfuck, now i'm gonna have to teabag you! I hate olive salad!
by DPdaix October 27, 2006
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Someone who claims to give their all in events/competitions but falls very short on the final day.
A lot of us spent all we had and went in to win. The Slackfucks just sat near the bottom, made excuses and were only in it for a prize and a free ride.
by 2foothead July 28, 2014
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