Antonyms of verb strengthen

2 of 3 senses of strengthen

Sense 1
strengthen, beef up, fortify -- (make strong or stronger; "This exercise will strengthen your upper body"; "strengthen the relations between the two countries")
       Antonym of weaken (Sense 1)
      => weaken -- (lessen the strength of; "The fever weakened his body")

Sense 2
strengthen -- (gain strength; "His body strengthened")
       Antonym of weaken (Sense 2)
      => weaken -- (become weaker; "The prisoner's resistance weakened after seven days")

Synonyms/Hypernyms (Ordered by Estimated Frequency) of verb strengthen

3 senses of strengthen

Sense 1
strengthen, beef up, fortify -- (make strong or stronger; "This exercise will strengthen your upper body"; "strengthen the relations between the two countries")
       => change, alter, modify -- (cause to change; make different; cause a transformation; "The advent of the automobile may have altered the growth pattern of the city"; "The discussion has changed my thinking about the issue")

Sense 2
strengthen -- (gain strength; "His body strengthened")
       => change -- (undergo a change; become different in essence; losing one's or its original nature; "She changed completely as she grew older"; "The weather changed last night")

Sense 3
tone, tone up, strengthen -- (give a healthy elasticity to; "Let's tone our muscles")
       => exercise, work out -- (do physical exercise; "She works out in the gym every day")