Refers to the waxing (☽) or waning (☾) crescent moon.
Note: This tag should only be used for the celestial body.
Example:
post #2294094
post #2300437
Posts like these don't fall under this tag:
post #2303367 (crescent hair ornament)
post #2216416 (crescent earrings and crescent necklace)
This tag implicates moon (learn more).