Entry 2 senses · 2 variants Webster, 1913 lessening · IPA /lˈɛsənɪŋ/ adj. n. 01 adj. becoming less in dimension or degree; as, the lessening distance between us. 1. becoming less in dimension or degree; as, the lessening distance between us. 02 n. a change downward; a decrease; a reduction. 1. a change downward; a decrease; a reduction. Syn. decrease, drop-off.