Definition of processionary
noun (also processionary moth) (plural processionaries)
a greyish moth whose caterpillars live communally in silken tents in trees, marching out at night in procession to feed, causing substantial damage.
- Family Thaumetopoeidae: several species, in particular the European pine processionary (Thaumetopoea pityocampa)
(also processionary caterpillar) the larva of the processionary moth.