There are multiple definitions:

1. measurement method ontology(English)

   • CMO, XCO, RGD
   • Biology, Classification
   • https://doi.org…/2041-1480-4-26
   • http://bioporta…ontologies/1584

2. maximum mouth opening(English)

   • proportional to the body size
   • Anatomy, Dentistry, Pediatrics
   • https://doi.org…79/crn.2008.025