a lesser Jewish festival, lasting eight days from the 25th day of Kislev (in December) and commemorating the rededication of the Temple in 165 bc by the Maccabees after its desecration by the Syrians. It is marked by the successive kindling of eight lights.
from Hebrew ḥănukkāh 'consecration'
Hanukkah in other Oxford dictionaries
Definition of Hanukkah in the US English dictionary