Definition - en passant

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
en pas•sant
ɑn pæ-sɑnt; Fr. ɑ̃ pɑsɑ̃
Pronunciation [ahn pa-sahnt; Fr. ahn pah-sahn]
–noun
1. French. in passing; by the way.
2. Chess. a method by which a pawn that is moved two squares can be captured by an opponent's pawn commanding the square that was passed.
Origin: 1655–65

Cambridge Advanced Learner's Dictionary
/,ɒ̃.pæs.ɒ̃/ /,ɑ̃ː.pæ’sɑ̃ː/ adv formal
If you say something en passant, you mention something quickly while talking about something else
She mentioned, en passant, that she'd been in Brighton the previous week.

Webster's 1913 Dictionary
En` pas`sant´
1. (Chess) In passing; in the course of any procedure;

WordNet Dictionary
Adv. 1. en passant - incidentally; in the course of doing something else; "he made this remark in passing"
Synonyms: in passing