compartment UK /kəmˈpɑːtmənt/US /kəmˈpɑɹtmənt/noun 5verb 1forms 3 noun5 •A room, or section, or chamber, typically within a vehicle.Two men were seated in a well-lit compartment of a third-class railway carriage. •One of the parts into which an area is subdivided. •A region in the body, delimited by a biological membrane. •The part of a protein that serves a specific function. •A mound (often of grass), shelf (of e.g. wall) or other thing beneath the shield in a coat of arms on which the supporters stand. verb1 •To arrange in separate compartments. formscompartmented · compartmenting · compartments