1. To make worse, to worsen, to make more severe; to intensify, to inflame, to irritate, to increase, and to heighten: "Don't scratch because you will only aggravate the itch."
2. To annoy, to exasperate, to anger, to vex, to nettle, and to affront: "His bossy attitude aggravates me."

Aggravate really means to make worse: "The cold weather aggravated his rheumatism." For a long time, many teachers and critics said the word should not be used to mean to irritate, to annoy, or to vex. Today this use is considered acceptable by a vast majority of teachers, critics, and linguists; therefore, you may say, or write, "Stop aggravating me" without feeling guilty.

Word History

The Latin word gravis means "heavy", and aggravare means "to make heavy". From the past participle aggravatus, the English language borrowed aggravate, "to make heavy, weighty, serious, grievous".

Then the sense was transferred from the thing which is made grievous to the person who is annoyed by it, and aggravate acquired the sense of "to provoke, to annoy", sometimes thoughtlessly used in a flippant sense; such as, an "aggravating shoestring".