A verbalisation of the female genital spasm (specifically, the 'awakening' of the clitoris) that is often experienced upon seeing something that is sexually pleasing.
Said typically from one woman to another, *clit twitch* is the mutual understanding of the level of excitement associated with the topic. A *clit twitch* can be associated with men, food, drugs or a scenario.
Female Roommate 1 to Female Roommate 2:
FR1: 'Hey, I thought maybe we would order Pizza and watch a movie tonight'
*After experiencing a long and tiring day*
FR1: (after chuckling appropriately) 'Pizza and Movies it is then'
Example 2: Men
Female Friend 1 to Female Friend 2
FF1: 'So incredibly hot guy is coming to the party tonight'
*Horny and turned on by said male party guest*
FF2: 'Oh my God, incredibly hot guy is going? God he is gorgeous, like actually, "*clit twitch*"