Noah Webster's New International Dictionary of the English Language

1. (n.) Active strength or force of body or mind; capacity for exertion, physically, intellectually, or morally; force; energy.

2. (n.) Strength or force in animal or force in animal or vegetable nature or action; as, a plant grows with vigor.

3. (n.) Strength; efficacy; potency.

4. (v. t.) To invigorate.