season vs Christmastime

season and Christmastime both are nouns.

Word	Noun	Adjective	Verb	Adverb
season	Yes	No	Yes	No
Christmastime	Yes	No	No	No

As nouns, Christmastime is a hyponym of season; that is, Christmastime is a word with a more specific, narrower meaning than season:

season (noun)	Christmastime (noun)
one of the natural periods into which the year is divided by the equinoxes and solstices or atmospheric conditions	period extending from Dec. 24 to Jan. 6
a recurrent time marked by major holidays
a period of the year marked by special events or activities in some field

season (verb)	Christmastime (verb)
make healthy
make more temperate, acceptable, or suitable by adding something else
lend flavor to