Entry 1 sense Webster, 1913 Undersell /ŭn'-dẽrs-ĕlˌ/ · Un·der·sell · IPA /ˈʌndərsˌɛl/ 01 v. t. To sell the same articles at a lower price than; to sell cheaper than. 1. To sell the same articles at a lower price than; to sell cheaper than.