| Noun | 1. sheep-tick - wingless fly that is an external parasite on sheep and cattleMelophagus Ovinus, sheep ked, sheep tickhippoboscid, louse fly - bloodsucking dipterous fly parasitic on birds and mammalsgenus Melophagus, Melophagus - an arthropod genus of wingless flies including the sheep ked | | 2. sheep-tick - parasitic on sheep and cattle as well as humans; can transmit looping ill in sheep (acute viral disease of the nervous system); a vector for Lyme disease spirocheteIxodes ricinus, sheep tickhard tick, ixodid - ticks having a hard shield on the back and mouth parts that project from the headgenus Ixodes, Ixodes - type genus of the family Ixodidae |