Thighmonds are the hot, sticky result of any sexual encounter in which the "pull out" method of birth control is employed and the male finds his release spillng all over his partners upper legs. Essentially it is the southern hemispheres answer to "the pearl necklace" of the northern territories.
"I can't believe you slept with him. You did use protection. Right?"
"You're kidding, right?"
"Well, he said he'd wear a condom and then, before I knew what was happening, he sprayed me like an alley cat yelling 'Yeah, baby, yeah! Thighmonds are a girls best friend!' and then he fell asleep on top of me."
"You sure can pick 'em, can't you?"