Period  —n. 1 length or portion of time. 2 distinct portion of history, a person's life, etc. 3 time forming part of a geological era. 4 interval between recurrences of an astronomical or other phenomenon. 5 time allowed for a lesson in school. 6 occurrence of menstruation (often attrib.: period pains). 7 complete sentence, esp. One consisting of several clauses. 8 esp. Us a = *full stop 1. B colloq. Used at the end of a statement to indicate finality (i'm not going, period). —adj. Characteristic of some past period (period furniture). [greek hodos way]