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used to describe someone who is keen as/desperate or horny for sex so much they look like a naked man running with a hard on.

Also used to describe how much you want/wanted to have sex with a girl
haha you were so run-stiff over that girl on friday night you couldn't take your eyes off her!

yeah bro when I saw that bitch shaking dat ass she made me sooo run-stiff I just wanted to fuck her right then

dude I saw you talking to that girl it was so obvious you were running stiff for her

shit I'm feelin' run-stiff tonight bro lets go get some pussy!
by yo bama February 10, 2010
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