interglacial adjective 1noun 1forms 1 adjective1 •Occurring between glaciations (colloquially known as ice ages).Palaeoenvironmental evidence from northwest Europe indicates that the oligocratic phase of the interglacial cycle (Fig. 3.1) had begun by ca. 5K years BP. — 2014 noun1 •The relatively warm period between glacial periods.The climatic recession which produced Britain's last glaciers came rapidly to an end about 10,000 bp, as temperatures rose during the end of the protocratic phase of the present interglacial. — 2019 formsinterglacials