A theory, this being a termination of words denoting theory.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)

Usage examples:

I haven't a single ism
- The Valiants of Virginia by Hallie Erminie Rives
" And go back to London, and talk Jay out of her 'bus- ism
- This Is the End by Stella Benson
Don't think about Socialism or any other " ism
- The Ragged Trousered Philanthropists by Robert Tressell