Nonoxynol: Nonoxynol-9 is the most commonly encountered spermatocide in the United States. As with other spermatocides, it destroys spermatozoa; it kills sperm.
The nonoxynols, technically speaking, are nonionic surfactant [surface active] mixtures that vary in the number of repeating ethoxy groups. They are much used as detergents, emulsifiers, wetting and defoaming agents, etc.
Nonoxynol-9 has 9 repeating ethoxy groups. It is the active component of most vaginal foams and creams.