WordWeb Online

1. Make strong or stronger
   "This exercise will strengthen your upper body"; "strengthen the relations between the two countries"
   - beef up, fortify
    
2. Gain strength
   "His body strengthened"
    
3. Give a healthy elasticity to
   - tone, tone up

Derived forms: strengthened, strengthening, strengthens

See also: strengthener, strengthening

Type of: alter, change, exercise, modify, work out

Antonym: weaken