a pernicious and malign influence that is hard to get rid of; "racism is a pestilence at the heart of the nation"; "according to him, I was the canker in their midst"
a small usually single-celled asexual reproductive body produced by many nonflowering plants and fungi and some bacteria and protozoans and that are capable of developing into a new individual without sexual fusion; "a sexual spore is formed after the fusion of gametes"