1. To corrupt, debase, or make impure by adding a foreign or inferior substance; often by replacing valuable ingredients with inferior ones; mixed with impurities: A restaurant was accused of adulterating their wine with water.

There are those who adulterate coffee with ground acorns or have silver debased or adulterated with copper.

3. Etymology: "to corrupt" from Latin adulteratus, past participle of adulterare, "to falsify, to corrupt"; from alterare, "to change, to alter".