A sex move where a woman (or man if thats what floats your boat)is in the process of doing squats at the gym and she realizes that she needs a spotter; thats where the man comes in. The man is sitting nude, fully erect on a three legged stool under the woman. Holding the womans ta ta's for support, the man gets ready to enter. When the woman comes down with her squat, the man penetrates, trying not to fall over on account of the three legged stool being wobbly.
The woman should have as little weight as possible when she is doing squats, to speed it up a little.
"Three legged" in this move has a double meaning if you catch my drift.
FREDRICO: "Dude! I three legged spot n' squated this chick at the gym last night!!"
STAVROS: "haHA, nice"