endospore en·do·spore (ěn'də-spôr')
A small spore formed within the vegetative cells of some bacteria.
A fungus spore borne within a cell or within the tubular end of a sporophore.
The inner layer of the wall of a spore.
A rounded, inactive form that certain bacteria assume under conditions of extreme temperature, dryness, or lack of food. The bacterium develops a waterproof cell wall that protects it from being dried out or damaged. Bacteria have been known to remain dormant but alive in the form of endospores for long periods of time, even thousands of years. Also called endosporium.