1. A woman who has remained single beyond the usual age of marrying.
2. In law, a woman who has never married.
3. A woman whose occupation is spinning.
From Middle English spinnestere (a woman who spins), from the fact that in earlier times spinning yarn was one of the jobs done by an unmarried woman.
And a thought:
Writing is like driving a car at night. You can only see as far as the headlights, but you make the whole trip that way. -E.L. Doctorow, writer (b. 1931)