plica sublingualis

noun

plica sub·​lin·​gua·​lis -ˌsəb-(ˌ)liŋ-ˈgwā-ləs 

plural plicae sublinguales -(ˌ)lēz 

: a transverse fold of mucous membrane that is situated at the base of the tongue on either side of the frenulum, overlies the sublingual gland, and is studded with 10 or 12 openings of the ducts of Rivinus