en passant in Spanish

In passing, by the way, incidentally. [from early 17th c.]

(chess) Of a capture of an enemy pawn, by moving one's pawn to the square that the enemy pawn has just passed over.

(chess) A move in which a pawn captures an opposing pawn on the same rank immediately after the latter has moved forward two squares on its first move in the game, as if it had moved forward only one square.