1. generally any arch shaped structure (but often it refers to the arched roof of an anatomical space) • Hypernyms: body part 2. an arched bundle of white fibers at the base of the brain by which the hippocampus of each hemisphere projects to the contralateral hippocampus and to the thalamus and mamillary bodies • Syn: trigonum cerebrale • Hypernyms: fiber bundle, fibre bundle, fascicle, fasciculus • Part Holonyms: limbic system, visceral brain, limbic brain • Part Meronyms: carina fornicis