Process removing compounds and their metabolites from the body, usually through the kidneys (via urine) or in the feces. Unless excretion is complete, the accumulation of foreign substances can adversely affect normal metabolism.
Source:
PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1166 (https://doi.org/10.1515/pac-2016-1120)