D defs.my
Entry 4 senses Webster, 1913

Infectious

/ĭnˌ-fĕk'-shəs/ · In·fec·tious · IPA /ɪnˈfɛk.ʃəs/
01 a. Having qualities that may infect; communicable or caused by infection; pestilential; epidemic; as, an infectious fever; infectious clothing…
  1. 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.” Shak.
  2. 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.” Dryden.
  3. 3.
    Contaminating with illegality; exposing to seizure and forfeiture.(Law)
    “Contraband articles are said to be of an infectious nature.” — Kent.
  4. 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.
Syn. See Contagious.