from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A horse that does not win, place, or show in a race.
- n. A loser in a competition, as in an election: "had enough support to place him in the middle of the also-rans” ( George F. Will).
- n. One that has little talent or success: just an also-ran in the art world.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A person or animal who competed in a race but did not win.
- n. Figuratively, a loser; one soon to be forgotten.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a contestant who loses the contest
The phrase comes from the world of horse race betting wherein lists of winners would be published with all non-paying positions printed in a block under the heading 'Also Ran:'. (Wiktionary)