sphincter

UK: /ˈsfɪŋktə^r/ US: /ˈsfɪŋktɚ/ ,(sfingk′tər)

WordReference Random House Learner's Dictionary of American English © 2025

sphinc•ter /ˈsfɪŋktɚ/   n. [countable]

1. Anatomy a circular band of muscle that encircles and closes an opening of the body or one of its hollow organs.

WordReference Random House Unabridged Dictionary of American English © 2025

sphinc•ter  (sfingk′tər), n. [Anat.]

1. Anatomy a circular band of voluntary or involuntary muscle that encircles an orifice of the body or one of its hollow organs.

• Greek sphinkté̄r, equivalent. to sphing-, base of sphíngein to hold tight + -tēr suffix denoting agent
• Late Latin
• 1570–80;

sphinc′ter•al, sphinc•te•ri•al  (sfingk tēr′ē əl), sphinc•ter•ic  (sfingk ter′ik), sphinc•ter•ate  (sfingk′tər it, -tə rāt′), adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

sphincter / ˈsfɪŋktə/ noun

1. a ring of muscle surrounding the opening of a hollow organ or body and contracting to close it

Etymology: 16th Century: from Late Latin, from Greek sphinkter, from sphingein to grip tightly

ˈsphincteral adjective