someone who manages to enter and exit intimate situations with ninja-like stealth. also used to describe someone highly skilled in the art of sex.
-"at the beginning of the night i had no intention of bringing him home, but before i knew it we were in my bed."
-"my goodness! well, was he good?"
-"amazing. but after we were done i closed my eyes for a sec, and just like that he vanished without a trace."
-"ahh, a sexual ninja."