AD- n.
the d with the first letter of the word to which ad- is prefixed. It remains unchanged before vowels, and before d, h, j, m, v. Examples: adduce, adhere, adjacent, admit, advent, accord, affect, aggregate, allude, annex, appear, etc. It becomes ac- before qu, as in acquiesce.
ADULTERATE v. 2 definitions
To corrupt, debase, or make impure by an admixture of a foreign or a baser substance; as, to adulterate food, drink, drugs, coin, etc. The present war has . . . adulterated our tongue with strange words. Spectator.