acquiesce: (to agree)
If you really believe in something, you should speak up. You should not be swayed by the majority view and acquiesce when the subject comes up during the meeting.
acrimony: (bitterness, a rough and bitter manner)
They divorced after a long time's acrimony in their marriage.
acumen: (shrewdness)
His business acumen leads to a right decision at the right time.
adjudicate: (resolve, bring to an end, settle conclusively)
The president of the university adjudicated the disputes between the two departments with overlapping curriculum.
admonish: (warn strongly)
His boss admonished him for his frequent tardiness.
ad nauseam: (get sick of, to a sickening extent)
He had a few too many drinks and babbled on his Vietnam War stories ad nauseam.
ad valorem: (value add to tax; in proportion to the value of the goods taxed)
The imported merchandise is more expensive because of the ad valorem charges.