Meaning

verb corrupt, debase, or make impure by adding a foreign or inferior substance; often by replacing valuable ingredients with inferior ones

adjective mixed with impurities

originFrom Latin adulterātus (“adulterate, adulterated, defiled, polluted, counterfeited”), perfect passive participle of adulterō (“to adulterate, defile, commit adultery (with), counterfeit”) (see -ate (adjective-forming suffix)), from ad- (“to, in the direction of”) + alter (“other”) + -ō (verb-forming suffix), literally “to go after someone else”. Equivalent to adultery + -ate.

Etymology from Wiktionary, CC BY-SA 3.0