fix

   1. to make an illegal arrangement

   In standard usage, to mend or adjust. Fix as a verb or noun may involve bribery, damaging a rival, a gambling coup, etc.:

    To a Metropolitan policeman fix could only mean nothing other than a bribe. (Deighton, 1978)

    ... named in several of the White House tapes whom Nixon planned to 'fix' after he had been reelected. (Colodny and Gettlin, 1991)

    There's eight or nine races on the card... and the fix can be in any time somebody says so. (Chandler, 1953)

   2. American

   to castrate

   The treatment of domestic animals, which might, I suppose, consider it an illegal arrangement, or fix¹.

   3. an injection of illegal narcotics

   Usually heroin:

    Frank, had you had a fix? (Davidson, 1978, asking about narcotic use, not navigational verification)

   4. to kill

   Not an illegal arrangement if done in battle:

    One such desperado appeared in a ditch, ten yards from the house in which we were sitting. We fixed him. (Home, 1994 — the 'desperado' was a German soldier with a bazooka)