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 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.