aquatic
(adj) relating to water
arable
(adj) suitable for growing crops
arbiter
(n) one who can resolve a dispute, make and decision
arbitrary
(adj) based of factors that appear random
arbitration
(n) the process or act of resolving a dispute
arboreal
(adj) of or relating to trees
arcane
(adj) obscure, secret, known only by a few
archaic
(adj) of or related to an earlier period or time, outdated
archetypal
(adj) the most representative or typical example of something
ardor
(n) extreme vigor, energy, enthusiasm
arid
(adj) excessively dry
arrogate
(v) to take without justification
artifact
(n) a remaining piece from an extinct culture or place
artisan
(n) a craftsman
ascertain
(v) to perceive, learn
ascetic
(adj) practicing restraint as a means of self-discipline, usually religious
ascribe
(v) to assign, credit, attribute to
aspersion
(n) a curse, expression of ill-will
aspire
(v) to long for, aim toward
assail
(v) to attack
assess
(v) to evaluate
assiduous
(adj) hard working, diligent
assuage
(v) to ease, pacify
astute
(adj) very clever, crafty
asylum
(n) a place of refuge, protection, a sanctuary
(n) an institution in which the insane are kept
atone
(v) to repent, make amends
atrophy
(v) to wither away, to decay
attain
(v) to achieve, arrive at
attribute
(v) to credit, assign
(n) a facet or trait
atypical
(adj) not typical, unusual
audacious
(adj) extremely bold
audible
(adj) able to be heard
augment
(v) to add to, expand
auspicious
(adj) favorable, indicative of good things
austere
(adj) very bare, bleak
avarice
(n) excessive greed
avenge
(v) to seek revenge
aversion
(n) a particular dislike for something
balk
(v) to stop, block abruptly
ballad
(n) a love song
banal
(adj) dull, commonplace
bane
(n) a burden