滾瓜爛熟 [ㄍㄨㄣˇ ㄍㄨㄚ ㄌㄢˋ ㄕㄨˊ; gun3 gua1 lan4 shu2] lit. ripe as a melon that rolls from its vine (idiom); fig. to know fluently to know sth inside-out to know sth by heart ◄ ►