| aspirant | One who seeks earnestly, as for advancement, honors, place. |
| aspiration | An earnest wish for that which is above one's present reach. |
| aspire | To have an earnest desire, wish, or longing, as for something high and good, not yet attained. |
| assailant | One who attacks. |
| assassin | One who kills, or tries to kill, treacherously or secretly. |
| assassinate | To kill, as by surprise or secret assault, especially the killing of some eminent person. |
| assassination | Murderer, as by secret assault or treachery. |
| assay | The chemical analysis or testing of an alloy ore. |
| assent | To express agreement with a statement or matter of opinion. |
| assess | To determine the amount of (a tax or other sum to be paid). |
| assessor | An officer whose duty it is to assess taxes. |
| assets | pl. Property in general, regarded as applicable to the payment of debts. |
| assiduous | Diligent. |
| assignee | One who is appointed to act for another in the management of certain property and interests. |
| assimilate | To adapt. |
| assonance | Resemblance or correspondence in sound. |
| assonant | Having resemblance of sound. |
| assonate | To accord in sound, especially vowel sound. |
| assuage | To cause to be less harsh, violent, or severe, as excitement, appetite, pain, or disease. |
| astringent | Harsh in disposition or character. |
| astute | Keen in discernment. |
| atheism | The denial of the existence of God. |
| athirst | Wanting water. |
| athwart | From side to side. |
| atomizer | An apparatus for reducing a liquid to a fine spray, as for disinfection, inhalation, etc. |
| atone | To make amends for. |
| atonement | Amends, reparation, or expiation made from wrong or injury. |
| atrocious | Outrageously or wantonly wicked, criminal, vile, or cruel. |
| atrocity | Great cruelty or reckless wickedness. |
| attache | A subordinate member of a diplomatic embassy. |
| attest | To certify as accurate, genuine, or true. |
| attorney-general | The chief law-officer of a government. |
| auburn | Reddish-brown, said usually of the hair. |
| audacious | Fearless. |
| audible | Loud enough to be heard. |
| audition | The act or sensation of hearing. |
| auditory | Of or pertaining to hearing or the organs or sense of hearing. |
| augment | To make bigger. |
| augur | To predict. |
| Augustinian | Pertaining to St. Augustine, his doctrines, or the religious orders called after him. |
| aura | Pervasive psychic influence supposed to emanate from persons |
| aural | Of or pertaining to the ear. |
| auricle | One of the two chambers of the heart which receives the blood from the veins. |
| auricular | Of or pertaining to the ear, its auricle, or the sense of hearing. |
| auriferous | Containing gold. |
| aurora | A luminous phenomenon in the upper regions of the atmosphere. |
| auspice | favoring, protecting, or propitious influence or guidance. |
| austere | Severely simple; unadorned. |
| autarchy | Unrestricted power. |
| authentic | Of undisputed origin. |