What does "infectious" mean?

Infectious: 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.

Additional senses

  1. 2.(Law) Contaminating with illegality; exposing to seizure and forfeiture. Contraband articles are said to be of an infectious nature. Kent.
  2. 3.Capable of being easily diffused or spread; sympathetic; readily communicated; as, infectious mirth. The laughter was so genuine as to be infectious. W. Black.

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