A pawn formation that resembles the Greek letter "λ".
It commonly arises after the knight on f3 (or f6) is exchanged for the opponent's queen's bishop, resulting in doubled pawns.
A well-known example occurs in the Trompowsky Attack, where Black aims for a kingside fianchetto.
After Bxf6 and ...gxf6, the pawns on f6 and g7 form the characteristic λ-shaped pattern.
