'En passant' definitions:

Definition of 'en passant'

From: WordNet
adverb
Incidentally; in the course of doing something else; "he made this remark in passing" [syn: in passing, en passant]
noun
(chess) a chess pawn that is moved two squares can be captured by an opponent's pawn commanding the square that was passed

Definition of 'En passant'

From: GCIDE
  • En passant \En` pas`sant"\ [F.] In passing; in the course of any procedure; -- said specif. (Chess), of the taking of an adverse pawn which makes a first move of two squares by a pawn already so advanced as to threaten the first of these squares. The pawn which takes en passant is advanced to the threatened square. [Webster 1913 Suppl.]