aha

Short definition from Wiktionary

Interjection

1. 1
   An exclamation of understanding, realization, invention, or recognition.
2. 2
   An exclamation of surprise, exaltation, or contempt.

Noun

1. 1
   Initialism of alpha-hydroxy acid.
2. 2
   Initialism of Agricultural Holdings Act tenancy.

Proper noun

1. 1
   Initialism of American Heart Association: an American non-profit organization focusing on cardiovascular medical research, education and care.
2. 2
   Initialism of Agricultural Holdings Act.