frostier; frostiest
1 : cold enough to produce frost (a thin layer of ice)
a frosty night
2 : covered with frost
frosty windows
3 : unfriendly or cold
a frosty stare
We received a frosty welcome.
— frostily /ˈfrɑːstəli/ adverb
She was glaring frostily at us.
— frostiness noun [noncount]
There's some frostiness [=coolness] between them.
the frostiness of the night