Noah Webster's New International Dictionary of the English Language

1. (v. t.) To enlarge or increase in size, amount, or degree; as, to augment an army by reinforcements; rain augments a stream; impatience augments an evil.

2. (v. t.) To add an augment to.

3. (v. i.) To increase; to grow larger, stronger, or more intense; as, a stream augments by rain.

4. (n.) Enlargement by addition; increase.

5. (n.) A vowel prefixed, or a lengthening of the initial vowel, to mark past time, as in Greek and Sanskrit verbs.