En prise (from French "can be taken")  describes a piece or pawn exposed to a material winning capture by the opponent. This is either a hanging piece, a not defended pawn  , a piece attacked by a lower valuable attacker, or a piece or pawn defended insufficiently. Any least valuable attacker (LVA) would gain a positive score from a static exchange evaluator on the target square, which also applies to a knight defended by a pawn and attacked by bishop and rook, where the majority of attackers and a least valuable attacker of similar value makes the knight en prise.
With pins, overloading, and other tactical motives in mind, whether keeping or putting a piece en prise is a blunder or a sacrifice is a matter of search, the latter may require some depth left to differentiate.
- En prise - Glossary of chess from Wikipedia
- en prise - Wiktionary
- Earliest Occurrences of Chess Terms by Edward Winter
- En Prise - Chess Basics
- En prise from ChessBase News, April 13, 2012