INFEC'TIOUS, adjective Having qualities that may taint, or communicate disease to; as an infectious fever; infectious clothing; infectious air; infectious miasma.

1. Corrupting; tending to taint by communication; as infectious vices or manners.

2. Contaminating with illegality; exposing to seizure and forfeiture.

Contraband articles are said to be of an infectious nature.

3. Capable of being communicated by near approach.

Grief as well as joy is infectious