thiev·ish (thē′vĭsh) adj. 1. Given to thieving. 2. Of, similar to, or characteristic of a thief; furtive. thiev•ish (ˈθi vɪʃ) adj. 1. given to thieving. 2. of, pertaining to, or characteristic of a thief; sneaky: a thievish look. [1400–50] thiev′ish•ly, adv.