1. (verb)strengthen, beef up, fortify make strong or stronger Synonyms: tone, tone up, fortify, gird, build up, fort, spike, arm, beef up, lace, strengthen Antonyms: weaken
2. (verb)strengthen gain strength Synonyms: tone up, fortify, tone, beef up Antonyms: weaken
3. (verb)tone, tone up, strengthen give a healthy elasticity to Synonyms: intone, tone, tone up, strengthen, inflect, fortify, modulate, beef up, chant Antonyms: weaken