What is the meaning of Sigmoid?

Semi-circular, like the uncial or lunate sigma (similar to English C).

Curved in two directions, like the letter "S", or the Greek ς (sigma); having a serpentine shape.

Exhibiting logistic growth; having a graph that accelerates until it reaches a carrying capacity.

Relating to the sigmoid colon.

Ellipsis of sigmoid colon.

Ellipsis of sigmoid function.

sigmoid

sigmoid

Source: wiktionary.org