interstadial

A brief (1000 years), relatively warm period within a glacial, during which climate, glaciers, and sea levels are between glacial and interglacial extremes.

A period of glacier retreat as opposed to a "stadial" period of glacier advance.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.