Astral
Relating to the stars
Astringent
Binding, causing contraction
Astronomical
Enormously large or extensive
Astute
Wise, shrewd, keen
Asunder
Into parts, apart
Asylum
Place or refuge or shelter, protection
Atavism
Reversion to an earlier type
Atheistic
Denying the existence of God
Atrocity
Brutal dead
Atrophy
Waste away
Attain
Achieve or accomplish
Attentive
Alert and watchful
Attenuate
Make thin, weaken
Attest
Testify, bear witness
Attribute
Essential quality
Attrition
Gradual decrease in number
Atypical
Not normal
Audacious
Daring, bold
Audit
Examination of accounts
Auditory
Pertaining to the sense of hearing
Augury
Omen, prophecy
August
Impressive, majestic
Auspicious
Favoring success
Austere
Forbiddingly stern