In Commonwealth countries, poussin is a butcher's term for a young chicken, less than 28 days old at slaughter and usually weighing 400–450 grams but not above 750 grams . It is sometimes also called spring chicken, although the term spring chicken usually refers to chickens weighing 750–850 grams . The word is the French language term for the same thing. Normally a portion is a whole poussin per person.
In the United States, poussin is an alternative name for a small-sized cross-breed chicken called Rock Cornish game hen, developed in the late 1950s, which is twice as old and twice as large as the typical British poussin.