Pro*ces"sion*a*ry (?), a. [Cf. LL. processionarius, F. processionnaire.]
Pertaining to a procession; consisting in processions; as, processionary service.
Processionary moth Zool., any moth of the genus Cnethocampa, especially C. processionea of Europe, whose larvae make large webs on oak trees, and go out to feed in regular order. They are covered with stinging hairs.
© Webster 1913.