Douglas Harper's Etymology Dictionary
Wiktionary
interglacial
a. Occurring between ice ages. n. The relatively warm period between ice ages.
Wikipedia
Interglacial
An interglacial period (or alternatively interglacial) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene interglacial began at the end of the Pleistocene, about 11,700 years ago.
Usage examples of "interglacial".
The Acheulean sites at Abbeville are of the same age as the Holstein interglacial and would thus be about 330,000 years old.
The problem is we're still in the interglacial warming that began at the end of the last Ice Age, and that warming sends what we call a thermal pulse down through the polar ice sheets.