Substance which binds to cell receptors normally responding to naturally occurring substances and which produces a response of its own.
See also: antagonist
Source:
PAC, 1993, 65, 2003. 'Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)' on page 2011 (https://doi.org/10.1351/pac199365092003)