sterilise

To sterilise something is to kill every germ on it, so that nothing living is left. You sterilise a baby's bottles in boiling water, and the dentist sterilises the instruments before the next patient sits down.

It is stronger than clean and stronger than disinfect: disinfecting cuts the germs down, sterilising gets rid of all of them, which is why hospitals use steam under pressure rather than a wipe. The adjective is sterile — a sterile dressing, a sterile room. Said of an animal or a person, sterilise means something else entirely: to operate so that they cannot have young, which is what happens to a cat at the vet's. American English spells it sterilize.