mucous patch
nounMedical Definition of mucous patch
: a broad, flat, erosive lesion of secondary syphilis that occurs on moist skin or mucous membranes and is often marked by a yellowish discharge
During the secondary stage of syphilis, mucous patches, which have high concentrations of Treponema pallidum and are extremely infectious, might develop in the mouth. — The Journal of the American Medical Association, 24 Nov. 2004