When a man has a full erection, but it still isn't quite rock-hard.
Firm, yet squishy.
ex: He tried to put it in my butt, except he has a butter boner so it didn't penetrate.
by mbph666 October 12, 2010
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Dude I put my boner butter on her bread, and by bread I mean face, and by boner butter I mean jizz.
by MOTHAFUCKAILOVECHEESE February 5, 2009
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