1. armful - As much as can be held in the arm or arms.
2. armory - An arsenal.
3. aroma - An agreeable odor.
4. arraign - To call into court, as a person indicted for crime, and demand whether he pleads guilty or not.
5. arrange - To put in definite or proper order.
6. arrangement - The act of putting in proper order, or the state of being put in order.
7. arrant - Notoriously bad.
8. arrear - Something overdue and unpaid.
9. arrival - A coming to stopping-place or destination.
10. arrogant - Unduly or excessively proud, as of wealth, station, learning, etc.
11. arrogate - To take, demand, or claim, especially presumptuously or without reasons or grounds.
12. Artesian well - A very deep bored well. water rises due to underground pressure
13. artful - Characterized by craft or cunning.
14. Arthurian - Pertaining to King Arthur, the real or legendary hero of British poetic story.
15. artifice - Trickery.