The Collaborative International Dictionary
Sigmoid \Sig"moid\, Sigmoidal \Sig*moid"al\, a. [Gr. ???; ??? sigma + e'i^dos form, likeness: cf. F. sigmo["i]de.] Curved in two directions, like the letter S, or the Greek [sigmat].
Sigmoid flexure (Anat.), the last curve of the colon before it terminates in the rectum. See Illust. under Digestive.
Sigmoid valves. (Anat.) See Semilunar valves, under Semilunar.
Douglas Harper's Etymology Dictionary
"shaped like a C" (1660s) or "shaped like an S" (1786), from sigma (q.v.) + -oid. Especially of the flexure of the colon (1891).
Wiktionary
a. 1 (context geometry English) Curved in two directions, like the letter "S", or the Greek ς (sigma). 2 #Having a serpentine shape; resembling S or ʃ 3 # (context mathematics English) logistic curve; having a graph that accelerates until it reaches a carrying capacity 4 (context geometry archaic English) semi-circular, like the lunar sigma (similar to English C). 5 (context anatomy English) Relating to the sigmoid flexure of the large intestine. n. (context mathematics English) A function having a graph whose shape is sigmoid. See http://en.wikipedia.org/wiki/Sigmoid and ''Mathworld''http://mathworld.wolfram.com/SigmoidFunction.html.
WordNet
adj. curved in two directions (like the letter S)
of or relating to the sigmoid flexure in the large intestine [syn: sigmoidal]
Wikipedia
Sigmoid means resembling the lower-case Greek letter sigma (ς) or the Latin letter S. Specific uses include:
- Sigmoid function, a mathematical function
- Sigmoid colon, part of the large intestine or colon
- Sigmoid sinus, two structures that drain blood from the bottom of the brain
- Sigmoid arteries, a pair/trio of arteries in the lower abdomen
Usage examples of "sigmoid".
Chapman mentions a case in which the liver was displaced by dilatation of the sigmoid flexure.
The lower half of the ascending frontal convolution, the greater half of the sigmoid gyrus, the posterior third of the lower and middle frontal convolutions, the base and posterior end of the upper convolution, and the base of the corresponding portion of the falciform lobe were involved.
After suffering from invagination of the bowel and inflammation of the ovarian tissue, an ovary was discharged through an opening in the sigmoid flexure, and thence expelled from the anus.
One male summer complaint found Doggy performing a sigmoidoscopy, that is, an examination of the rectum and sigmoid colon.
Indeed (as I'd rather hoped) the little mystery so intrigued him that he gave over his heavy-breathed inspection of my sigmoid colon.
What gross colonic events, may I ask, are taking place in the area of my sigmoid flexure, Softly thought, stressing to himself the importance of such inquiries, Mainwarì.