= infectious, adj. 6.

Now chiefly in predicative use. Of a disease: capable of spreading from one individual to another; infectious; contagious.

Of an action, emotion, etc.: having the quality of spreading from one to another; easily communicable. Also (of a person): attractive, compelling.

figurative. Apt to be communicated from one to another or to others. (Cf. catching, adj. 2, infectious, adj. 6.)