Definition from Wiktionary, the free dictionary
sphincter (plural sphincters)
- (anatomy) A ringlike band of muscle that surrounds a bodily opening, constricting and relaxing as required for normal physiological functioning.
- the sphincter of the bladder
- 1982, Lawrence Durrell, Constance (Faber & Faber, 2004: Avignon Quintet), page 836:
- She decided that she would force him to climax first by the sheer strength of her young animal control, the strength of her sphincters […]
- (in particular) The internal or external anal sphincter, to the extent these are distinguished as two separate entities.
Derived terms 
Terms derived from the noun "sphincter"
Related terms 
band of muscle