old maid: a single woman regarded as too old for marriage. Source
spinster: a woman who is not married, especially a woman who is no longer young and seems unlikely ever to marry. Source
These 2 above words refer to female, but now I want to find the similar term for male.
You can say that we can use "unmarried man" which is similar to "unmarried woman"
However, unmarried woman is "a woman who is not married" Source and it does not have the connotation as of "old maid" or "spinster".
It is because that "unmarried woman" could be the sister in a church who just do not want to marry because her religion. On the contrary, "old maid" or "spinster" means she is not attractive enough to get a husband or noone wants to marry her.
Best Answer
Confirmed bachelor doesn't necessarily have the same connotation of "not being attractive enough," but it does indicate a sense of permanence. It sometimes is a euphemism for homosexuality, but more generally:
A couple more:
As mentioned, homosexuality can be implied, but it is by no means the only way to understand this. For example, a Washington Post headline reads:
But Graham is not openly gay, and the Post is not insinuating that.