Entry 1 sense Webster, 1913 Implausible /ĭmˌ-plôz'-əb-əl/ · Im·plau·si·ble · IPA /ˌɪmplˈɔzəbəl/ 01 a. Not plausible; not wearing the appearance of truth or credibility, and not likely to be believed. 1. Not plausible; not wearing the appearance of truth or credibility, and not likely to be believed.