The pair of tongs sex position is a standing, side-entry sex position, where a standing person penetrates their partner who lies in a side plank. It's thought that it gets its name because the participants' straight, interlocking legs look like a pair of tongs. It's known as an extreme sex position for its high degree of difficulty and athleticism.
It should not be confused with the Kama Sutra term of the same name, which is a sexual technique rather than a position.