Tick, n.  Zool. (a) Any one of numerous species of large parasitic mites which attach themselves to, and suck the blood of, cattle, dogs, and many other animals. When filled with blood they become ovate, much swollen, and usually livid red in color. Some of the species often attach themselves to the human body. The young are active and have at first but six legs. (b) Any one of several species of dipterous insects having a flattened and usually wingless body, as the bird ticks (see under Bird) and sheep tick (see under Sheep).
 Tick bean, a small bean used for feeding horses and other animals.
 Tick trefoil Bot., a name given to many plants of the leguminous genus Desmodium, which have trifoliate leaves, and joined pods roughened with minute hooked hairs by which the joints adhere to clothing and to the fleece of sheep.