strengthen 5 antonyms and opposites of strengthen. Verb — To make something stronger, more solid, or more effective. Synonyms for strengthen anneal brace build up confirm enstrengthen fortify harden intend indurate munite invigorate nerve nerve up reinforce roborate steel strength thicken Antonyms for strengthen weaken atrophy debilitate enervate enfeeble ← Back to the full definition of strengthen
