boo stank Share definition Flag a guy or girl who is not your "significant other" but you have sex with and he/she is your best bud. ie. boo stank, baby boy, cut buddy, buddy, bae, baby etc boo stank by Killa Cat August 21, 2011 0 0 Get merch Get the boo stank mug. Buy Now — $32.95 See more merch