Very cold, chilly. A temperature that makes one shiver. Usually applied to the weather or outdoor temperature. The cold temperature may be accompanied by a cold wind that goes right through ones clothing. The same kind of cold as 'brass monkeys' weather. Can also be applied (typically sarcastically) to indoor temperatures, especially if it is colder than is comfortable and one wants to influence a change!
Used in the North of Britain.
It's brassic out (there).
Brrrr, it's a bit brassic out there. ('a bit' can be added as an under-exaggeration)