Simple Definition:

Aspirate is a linguistic term used to describe a speech sound that is produced with a strong burst of air ([exhaling forcefully]), typically at the beginning of a word. It is commonly found in languages like English and Greek. For example, the “h” sound at the beginning of the word “hat” is an aspirate.

Very Simple Definition:

Aspirate is a strong burst of air that we make when we say some words. Like when we say “hat,” we blow out air at the beginning.