A chemical compound which conceals the presence of a substance within the body; (Sport) a drug taken to mask the presence of a banned substance in urine, etc.
Origin
1970s; earliest use found in The Washington Post.
Definition of masking agent in US English:
masking agent
noun
A chemical compound which conceals the presence of a substance within the body; (Sport) a drug taken to mask the presence of a banned substance in urine, etc.