- indoleacetic acid, IAA - a plant hormone promoting elongation of stems and roots
--1 is a kind of auxin
- Islamic Army of Aden, IAA, Islamic Army of Aden-Abyan, Aden-Abyan Islamic Army - Yemen-based terrorist group that supports al-Qaeda's goals; seeks to overthrow the Yemeni government and eliminate United States interests; responsible for bombings and kidnappings and killling Western tourists in Yemen
--2 is a kind of terrorist organization, terrorist group, foreign terrorist organization, FTO