1. abstruse - Dealing with matters difficult to be understood.
2. absurd - Inconsistent with reason or common sense.
3. abundant - Plentiful.
4. abusive - Employing harsh words or ill treatment.
5. abut - To touch at the end or boundary line.
6. abyss - Bottomless gulf.
7. academic - Of or pertaining to an academy, college, or university.
8. academician - A member of an academy of literature, art, or science.
9. academy - Any institution where the higher branches of learning are taught.
10. accede - To agree.
11. accelerate - To move faster.
12. accept - To take when offered.
13. access - A way of approach or entrance; passage.
14. accessible - Approachable.
15. accession - Induction or elevation, as to dignity, office, or government.