What is the meaning of prophylactic?

noun

• Remedy that prevents or slows the course of an illness or disease.
  • usage: "the doctor recommended several preventatives"
  • synonyms: preventive, preventative
• Contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse.
  • synonyms: condom, rubber, safety, safe

adjective

• Capable of preventing conception or impregnation.
  • usage: "contraceptive devices and medications"
  • synonyms: contraceptive, antifertility
• Warding off."the swastika... A very ancient prophylactic symbol occurring among all peoples- Victor Schultze
  • synonyms: cautionary
• Preventing or contributing to the prevention of disease.
  • usage: "preventive medicine"; "vaccines are prophylactic"; "a prophylactic drug"
  • synonyms: preventive, preventative