1. make strong or stronger

- This exercise will strengthen your upper body

- strengthen the relations between the two countries

Similar word(s): fortify

Definition categories: change, alter, modify

2. gain strength

- His body strengthened

Definition categories: change

3. give a healthy elasticity to

Similar word(s): tone

Definition categories: body, exercise

Sentences with strengthen as a verb:

- to strengthen a limb, a bridge, an army;  to strengthen an obligation; to strengthen authority