Sterilise is a term used to describe the process of making something free from bacteria or other microorganisms. SPAY, which has four letters, is the process of removing the reproductive organs of a female animal. DISINFECT, which has nine letters, is the process of using chemicals or heat to kill bacteria and other microorganisms. IRRADIATE, also with nine letters, is the process of exposing something to radiation in order to sterilise it. EMASCULATE, with ten letters, is the process of removing the male reproductive organs. CASTRATE, with eight letters, is the process of removing the testicles of a male animal. NEUTER, with six letters, is the process of removing the reproductive organs of an animal, usually a male. GELD, with four letters, is the process of removing the testicles of a male horse. All of these processes are used to sterilise something and make it free from bacteria or other microorganisms.