Definition of "four-membered" []

• Of a chemical compound having a ring with four members (adjective)

WordNet. Princeton University. 2010.

• "Others were equally sure it was a four-membered ring fused to a five-membered ring, known as a beta lactam."
• "The double door frame projects pilaster-like, with a four-membered cornice above, from which rises an elliptical arch, with an elliptical cornice about a foot above."
• "OXE has an unstable chemical structure (a four-membered ring containing three carbons and one oxygen) that makes it prone to being split open."