The term 'coop pigeon' refers to a type of domesticated bird kept for its eggs, meat, or feathers. The crossword solutions for this term are COO (3 letters), COOS (4 letters), HEN (3 letters), and HENS (4 letters). COO is an abbreviation for the word 'COOPERATE, ' which is what the birds do when they live in a coop. COOS is the plural form of the word 'COO, ' which is the sound that pigeons make. HEN is the female of the species, and HENS is the plural form of the word.