ˈ ̷ ̷ ̷ ̷ at iso- +ˌpag noun
( -s )
Etymology: is- + -pag (from Greek pagos frost; akin to Greek pēgnynai to fasten) — more at pact
: an equiglacial line on a map or chart that connects the points where ice is present for approximately the same number of days in winter