unassertiveEnglishOxford American Thesaurusunassertive adjective she seemed unassertive and lacking confidence: passive, retiring, submissive, unassuming, self-effacing, modest, humble, meek, unconfident, unforthcoming, diffident, shy, timid, timorous, shrinking, hesitant, insecure, unsure; informal mousy. ▷antonyms assertive, bold.