ves·tig·i·al / veˈstij(ē)əl/ • adj. forming a very small remnant of something that was once much larger or more noticeable: he felt a vestigial flicker of anger from last night. ∎  Biol. (of an organ or part of the body) degenerate, rudimentary, or atrophied, having become functionless in the course of evolution: the vestigial wings of kiwis are entirely hidden.DERIVATIVES: ves·tig·i·al·ly adv.

vestigial (ves-tij-iăl) adj. existing only in a rudimentary form. The term is applied to organs whose structure and function have diminished during the course of evolution.