a. - Having qualities that may infect; communicable or caused by infection; pestilential; epidemic; as, an infectious fever; infectious clothing; infectious air; infectious vices.
a. - Corrupting, or tending to corrupt or contaminate; vitiating; demoralizing.
a. - Contaminating with illegality; exposing to seizure and forfeiture.
a. - Capable of being easily diffused or spread; sympathetic; readily communicated; as, infectious mirth.