1.
If someone describes a town as a one-horse town, they mean it is very small, dull, and old-fashioned.
Would you want to live in a small, one-horse town for your whole life?
ADJ : ADJ n [ disapproval ]
2.
If a contest is described as a one-horse race, it is thought that one person or thing will obviously win it.
He described the referendum as a one-horse race...
ADJ : ADJ n