make (something) greater by adding to it; increase.
Merriam-Webster Online Dictionary
augment (verb)transitive verb
1.
to make greater, more numerous, larger, or more - intense the impact of the report was augmented by its timing
2.
to add an augment to - (see augment)
3.
intransitive verb
- supplement augmented her income to become - augmented increase
a vowel or a lengthening of the initial vowel to mark past time especially in Greek and Sanskrit verbs - prefixed