Synonyms for uncertain: Antonyms of uncertain: That which is uncertain is doubtful or problematical; The time of his arrival is uncertain. Meanings, translations, synonyms, pronunciations, examples, and grammar insights - all in one comprehensive guide. The meaning of uncertain is not known beyond doubt : See āmeaning & useā for definitions, usage, and quotation evidence. Volatile, unpredictable, changeful, unstable, inconsistent, variable, unsettled, capricious; How to use uncertain in a sentence. It often involves danger through an inability to predict or to place confidence in the unknown: Uncertain refers to something being unknown, doubtful, or not clearly identified or defined. Ā· uncertain (comparative more uncertain or (rare) uncertainer, superlative most uncertain or (uncommon) uncertainest) not known for certain; Not known or established; There are 19 meanings listed in oeds entry for the adjective uncertain, one of which is labelled obsolete. Not knowing what to do or believe, or not able to decide about something: Certain, constant, stable, predictable, steady, ā¦ Discover everything about the word uncertain in english: It can pertain to situations, events, or outcomes that are unpredictable or lack certainty. Uncertain synonyms, uncertain pronunciation, uncertain translation, english dictionary definition of uncertain.