In*fec"tious (?), a. [Cf. F. infectieux.]
1.
Having qualities that may infect; communicable or caused by infection; pestilential; epidemic; as, an infectious fever; infectious clothing; infectious air; infectious vices.
Where the infectious pestilence.
Shak.
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. Law
Contaminating with illegality; exposing to seizure and forfeiture.
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.
Syn. -- See Contagious.
© Webster 1913.