1. (a.) Having qualities that may infect; communicable or caused by infection; pestilential; epidemic; as, an infectious fever; infectious clothing; infectious air; infectious vices.

2. (a.) Corrupting, or tending to corrupt or contaminate; vitiating; demoralizing.

3. (a.) Contaminating with illegality; exposing to seizure and forfeiture.

4. (a.) Capable of being easily diffused or spread; sympathetic; readily communicated; as, infectious mirth.

catching communicable contagious deadly destructive endemic envenomed epidemial epidemic epiphytotic epizootic infective inoculable irresistible malign malignant mephitic miasmal miasmatic miasmic noxious pandemic pestiferous pestilent pestilential poisonous sporadic spreading sympathetic taking toxic toxicant toxiferous transmissible venenate veneniferous venenous venomous virulent zymotic