ボインボイン LinksSentence search for ボインボインSentence search for ぼいんぼいんEdit in JMdict Noun, Noun which may take the genitive case particle 'no'1. big breasts; big boobsSee also ぼいんNoun2. boing-boingsoundいとこ従姉妹にはね、ものすご凄いボインボインなこ子がいるんだよ?Among my cousins, you know, there's a girl with the most enormous breasts.Other formsぼいんぼいん Discussions Log in to talk about this word.