To increase; to make larger or supplement.

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

To grow; to increase; to become greater.

To slow the tempo or meter, e.g. for a dramatic or stately passage.

To increase an interval, especially the largest interval in a triad, by a half step (chromatic semitone).

(grammar) To add an augment to.

Increased in number, amount or strength.

Increased by a semitone.