fork-tailed \ˈ ̷ ̷| ̷ ̷\adjective orforktail\ˈ ̷ ̷ˌ ̷ ̷\ : having the tail or posterior end of the body deeply cleft < a fork-tailed schistosome cercaria > usually: having the outer feathers or rays of the tail much longer than the central ones — used of birds and fishes