The phrase "glacial conditions" refers to extremely cold temperatures and harsh weather conditions, similar to those experienced in icy regions like glaciers. Full definition
A map of sea ice extent at the climax of the Last Glacial Maximum (both perennial and seasonal ice), prepared with the help of a colleague, makes it possible to discuss what genetic and fossil evidence can tell us about the probable effects of glacial conditions on polar bears and ringed seals. (polarbearscience.com)
Equilibrium sensitivity, including slower surface albedo feedbacks, is 6 °C for doubled CO2 for the range of climate states between glacial conditions and ice - free Antarctica.» (realclimate.org)
[Response: In our model they only occur under glacial conditions, not under Holocene conditions. (realclimate.org)