sphincter
From Longman Dictionary of Contemporary EnglishRelated topics: Humansphinctersphinc‧ter /ˈsfɪŋktə $ -ər/ noun [countable] medical HBHa muscle that surrounds an opening in your body, and can become tight in order to close the openingExamples from the Corpussphincter• The sphincters become leaky, and the urine overflows.• Thus it should not be assumed that older patients with ulcerative colitis have weaker sphincters than younger patients.Origin sphincter (1500-1600) Late Latin Greek, from sphingein “to tie tightly”