Entry 3 senses · 2 variants Webster, 1913 Overestimate /ōvˌ-ẽr-ĕs'-təm-ātˌ/ · O·ver·es·ti·mate · IPA /ˌəʊvəɹˈɛstɪmeɪt/ v. t. n. 01 v. t. To estimate too highly. 1. To estimate too highly. 2. To overvalue. 02 n. An estimate that is too high; as, an overestimate of the vote. 1. An estimate that is too high; as, an overestimate of the vote.