third favorite; possible winner
Horse-racing term for the horse expected to place third, often used in betting contexts alongside 本命 (favorite) and 対抗 (second favorite).
The third-favorite horse ran better than expected and finished second.
I check the horses marked as third favorites in the racing newspaper.
Compound of 単 (single, simple) and 穴 (hole, gap). The exact origin is uncertain, but it likely derives from the idea of a 'single hole' or 'one gap' in the betting odds, indicating a horse that is not the top favorite but still has a chance to win.