Verb

1. To increase, make larger or supplement.

   The money from renting out a spare room can augment a salary.

2. To slow the tempo or meter, e.g. for a dramatic or stately passage.
3. To increase an interval by a half step (chromatic semitone).
4. To increase the largest interval in a triad, especially a fifth or a sixth, by a half-step (chromatic semitone).

Noun

1. In some Indo-European languages, a prefix e- (a- in Sanskrit) indicating a past tense of a verb.