Merriam-Webster Online Dictionary
against (preposition)1.
a) in opposition or hostility to - spoke against his enemies
b) contrary to - against the law
c) in competition with - racing against each other
d) as a basis for disapproval of - had nothing against him
2.
a) directly opposite - facing she sat down just over against me Daniel Defoe
b) obsolete exposed to
3.
compared or contrasted with - profits are up against last year
4.
a) in preparation or provision for - saving against an uncertain future
b) as a defense or protection from - a shelter against the cold
5.
a) in the direction of and into contact with - knocked against the ropes
b) in contact with - leaning against the wall
6.
in a direction opposite to the motion or course of counter to - sail against the wind
7.
a) as a counterbalance to - weighing risk against profit
b) in exchange for - a lower rate against the dollar
c) as a charge on - charged against her account
8.
before the background of - viewed against the sky
archaic in preparation for the time when - throw on another log of wood against father comes home Charles Dickens
Merriam-Webster Online Thesaurus
against (preposition)1.
in or into contact with
SYNONIMS:
on, uponRELATED WORDS:
alongside, next, next to; upside2.
opposed to; not for
SYNONIMS:
against, agin, contraRELATED WORDS:
athwart, contrary to; versus, with