oil·y / ˈoilē/ • adj. (oil·i·er, oil·i·est) 1. containing oil: oily fish such as mackerel and sardines. ∎ covered or soaked with oil: an oily rag. ∎ resembling oil in appearance or behavior: the oily swell of the river.2. fig. (of a person or their behavior) unpleasantly smooth and ingratiating: his oily smile.DERIVATIVES: oil·i·ness n.