against

Etymology

Formed from Middle English ayenes, agenes, againes (“in opposition to”), a southern variant of agen, or directly from again, either way with adverbial genitive singular ending -es; the parasitic -t was added circa 1350, probably by confusion with the superlative ending -est. Surface analysis again + -st (excrescent ending).

prep

1. In a contrary direction to.
   It is hard work to swim against the current.
2. In physical opposition to; in collision with.
   The rain pounds against the window.
   Ivor had acquired more than a mile of fishing rights with the house ; he was not at all a good fisherman, but one must do something ; one generally, however, banged a ball with a squash-racket against a wall. 1922, Michael Arlen, “3/19/2”, in “Piracy”: A Romantic Chronicle of These Days
3. In physical contact with, so as to abut or be supported by.
   The ladder was leaning against the wall.
   The puppy rested its head against a paw.
   The kennel was put against the back wall.
4. Close to, alongside.
   A row of trees stood against a fence.
5. In front of; before (a background).
   The giant was silhouetted against the door.
6. In contrast or comparison with.
   He stands out against his classmates.
   This report sets out the risks against the benefits.
7. In competition with, versus.
   The Tigers will play against the Bears this weekend.
   The breakthrough came through Torres who, pilloried for his miss against Manchester United a week earlier, scored his second goal of the season. September 24, 2011, Aled Williams, “Chelsea 4-1 Swansea”, in BBC Sport
8. Contrary to; in conflict with.
   Doing this is against my principles.
   It is against the law to smoke on these premises.
   There was no car in sight so we crossed against the red light.
9. In opposition to.
   Are you against freedom of choice?
   He waged a ten-year campaign against the company that was polluting the river.
   I'd bet against his succeeding.
   (with implied object) Ten voted for, and three voted against.
   Plant breeding is always a numbers game.[…]The wild species we use are rich in genetic variation,[…]. In addition, we are looking for rare alleles, so the more plants we try, the better. These rarities may be new mutations, or they can be existing ones that are neutral—or are even selected against—in a wild population. A good example is mutations that disrupt seed dispersal, leaving the seeds on the heads long after they are ripe. 2013 May-June, David Van Tassel, Lee DeHaan, “Wild Plants to the Rescue”, in American Scientist, volume 101, number 3
10. Of betting odds, denoting a worse-than-even chance.
    That horse is fifty-to-one against, so it has virtually no chance of winning.
11. In exchange for.
    The vouchers are redeemable against West End shows and theatre breaks.
12. As counterbalance to.
13. As a charge on.
    Tax is levied against income from sales.
14. As protection from.
    He turned the umbrella against the wind.
    Monoclonal antibodies were raised against these proteins: IN-1 and IN-2 bound both to the 35 kd and 250 kd inhibitors and to the surface of differentiated cultured oligodendrocytes. March 1, 1988, Pico Caroni, Martin E. Schwab, “Antibody against myelin associated inhibitor of neurite growth neutralizes nonpermissive substrate properties of CNS white matter”, in Neuron, →DOI, page 85
15. In anticipation of; in preparation for (a particular time, event etc.).
    The stores are kept well stocked against a time of need.
    Rod, who always distrusted such methods, was forced to accept the new way but had begun to stash away large amounts of cash against the day that the system might be sabotaged or failed entirely. 2003, Rodger J. Bille, A Few of the Chosen: Survivors of Terrorism, Trafford Publishing, page 8
16. (Hollywood) To be paid now in contrast to the following amount to be paid later under specified circumstances, usually that a movie is made or has started filming.
    The studio weren't sure the movie would ever get made, so they only paid $50,000 against $200,000. That way they wouldn't be out very much if filming never began.
    “Hollywood noises” yielded an early $35,000 option against $100,000 if the movie was made. 2011, Charles Foran, Mordecai: The Life & Times
17. (obsolete) Exposed to.

conj

1. (obsolete) By the time that (something happened); before.
   He now gave Mrs Deborah positive orders to take the child to her own bed, and to call up a maid-servant to provide it pap, and other things, against it waked. 1749, Henry Fielding, Tom Jones, Folio Society, published 1973, page 6