n. 1. The material or substance on which an enzyme acts. 2. Biology A surface on which an organism grows or is attached. 3. An underlying layer; a substratum. 4. Linguistics An indigenous language that contributes features to the language of an invading people who impose their language on the indigenous population. [From SUBSTRATUM.] |
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.