From Longman Dictionary of Contemporary Englishlong oddslong oddsPROBABLYif there are long odds against something happening, it is very unlikely that it will happen → long
Examples from the Corpus
long odds• Even with the delay, Lee now faces long odds.• Has slipped down the weights and could surprise at long odds here.• Highbrook will be at longer odds than she should be as a result of her defeat last time out at Newmarket.• Talbot would have taken long odds that he was cold sober.• Exactly thirty years after completing their only Wembley triumph, Leigh are at long odds to go all the way in 2001. 