Thesaurus.com Dictionary.com

unexpected winner

NOUN

dark horse

Synonyms

STRONGEST

also-ran long shot sleeper underdog

WEAK

hundred-to-one shot improbability little chance little opportunity outside chance outside shot poor bet poor lookout poor possibility poor prognosis poor prospect slim chance small chance stalking horse unknown unknown quantity unlikelihood unlikely winner upsetter

From Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.