Infectious /(?)/

In·fec·tious

Infectious

a.
  1. Having qualities that may infect; communicable or caused by infection; pestilential; epidemic; as, an infectious fever; infectious clothing; infectious water; infectious vices.
    Where the infectious pestilence.
  2. Corrupting, or tending to corrupt or contaminate; vitiating; demoralizing.
    It [the court] is necessary for the polishing of manners . . . but it is infectious even to the best morals to live always in it.
  3. Contaminating with illegality; exposing to seizure and forfeiture. (Law)
    Contraband articles are said to be of an infectious nature.
    — Kent.
  4. Capable of being easily diffused or spread; sympathetic; readily communicated; as, infectious mirth.
    The laughter was so genuine as to be infectious.
    — W. Black.