shape that resembles the moon before it reaches the first-quarter lunar phase, or after it passes the last quarter.

In art and symbolism, a crescent is generally the shape produced when a circular disk has a segment of another circle removed from its edge, so that what remains is a shape enclosed by two circular arcs of different diameters which intersect at two points (usually in such a manner that the enclosed shape does not include the center of the original circle).

An example of an artistically exaggerated crescent — in this case a large circle with a smaller one removed, as on the Turkish flag.
An astronomically correct crescent shape (in dark grey), complemented by a gibbous shape (in light grey).
Statue of the Crescent in one of the squares.

The crescent was long used as the symbol of Byzantium. Now it is the main symbol for the religion Islam.

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English Wiktionary
The English Wiktionary has a dictionary definition (meanings of a word) for: crescent