Entry 3 senses · 2 variants Webster, 1913 Eighteen /(ā"tēn`)/ · Eight·een · IPA /ˈeɪ(t).tin/ a. n. 01 a. Eight and ten; as, eighteen pounds. 1. Eight and ten; as, eighteen pounds. 02 n. The number greater by a unit than seventeen; eighteen units or objects. 1. The number greater by a unit than seventeen; eighteen units or objects. 2. A symbol denoting eighteen units, as 18 or xviii.