upwind vs against the wind

upwind is an adjective but against the wind is not an adjective.

Word	Noun	Adjective	Verb	Adverb
upwind	No	Yes	No	Yes
against the wind	No	No	No	Yes

As adverbs, upwind and against the wind are synonyms defined as:

upwind and against the wind: in the direction opposite to the direction the wind is blowing

Other synonyms of upwind include into the wind.

upwind (adjective)	against the wind (adjective)
towards the side exposed to wind

upwind (adverb)	against the wind (adverb)
in the direction opposite to the direction the wind is blowing	in the direction opposite to the direction the wind is blowing
away from the wind