Unmarriageable

You have always had a little way of alluding to her as an unmarriageable girl.

He had a way of pronouncing the word "miss" that made it an epithet, a sneer at her unmarried and unmarriageable state.

A link was wanting between two craving parts of nature, and he was hurled into being as the bridge over that yawning need, the mediator betwixt two else unmarriageable facts.

[…] which is a very curious cross between two things that at first sight may seem unmarriageable, the Wordsworthian enthusiasm and the Byronic despair.