when u get a throbbing tingly sensation... all around your body. makes you wanna pee. usually when thinking about people of the opposite sex, often thinking about touching him/her. or reading/watching/ or hearing about people making love. it's utterly amazing.
when he took off his shirt and went to kiss me i got cuz.
when i was reading "the notebook" the author was really descriptive about them having sex, i got cuz.