Definition of ally :
1. A relative; a kinsman.
2. Anything akin to another by structure, etc.
3. Anything associated with another as a helper; an auxiliary.
4. One united to another by treaty or league; - usually applied to sovereigns or states; a confederate.
5. See Alley, a marble or taw.
6. To connect or form a relation between by similitude, resemblance, friendship, or love.
7. To unite, or form a connection between, as between families by marriage, or between princes and states by treaty, league, or confederacy; - often followed by to or with.
henchman, link, federate, protagonist, bind, champion, abetter _or_ abettor, retainer, coadjutor, accessory, align, attendant, follower, admirer, politics, combine, conjoin, booster, league, participator, helper
co-operate (part of speech: verb)
friend (part of speech: noun)
company, friend, roommate, pal, sister, companion, chum, familiar, playmate, acquaintance, schoolmate, confidant, fellow, comrade, brother, intimate, classmate, partner, crony, co-worker, cousin, teammate, buddy, amigo, mate
join (part of speech: verb)
confederate (part of speech: noun)
- " You want some revenge for Ally! - "Helena Brett's Career", Desmond Coke.
- They hastened at once to another step to ally Missouri with the South. - "The Struggle for Missouri", John McElroy.
- It is, no doubt, in regard to a champion so formidable, both as ally and as enemy, difficult to write without fear or favour, but it must be attempted. - "A History of English Literature Elizabethan Literature", George Saintsbury.