dust: adjective and noun, idiot, idiotic, can be used quite playfully or harshly.

flink: adjective, clever, good.

garra: adjective, guaranteed.

gira: adjective, geared, f.x. to be geared up (for something).

grandis: noun, Norway’s most popular pizza, short for Pizza Grandiosa. I always thought this was a type of ice-cream! :P

gretten: adjective, grumpy, f.x. Isak can be a bit gretten.

greie: noun, a thing, literally an unspecified thing.

grei: adjective, cosy <--when describing a person. Can also be used to describe a noun (thing) as being ok, f.x. det er greit, that is okay.

gæren: adjective, crazy, mad.

herregud: like saying oh my God.

homse: adjective and noun, gay, homo. I don’t know if it’s the same in Norwegian, but in Danish, it’s not a nice word to use to describe someone as gay; it’s quite a negative word. So when calling someone gay in Danish homoseksuel is better. (fun fact)

hooke: verb, to hook up with.

jævla/ jævlig: adverb, fucking. Used to emphasis something.

keen: adjective, keen. Literally means keen (I dunno why I used it sorry).

kjekk: adjective, physically attractive, mostly used for a guy.

kjekkas: noun, a physically attractive guy.

klein: adjective, embarrasing or hungover. Klein means awkward in Norwegian. If translated, embarrassing would be pinlig, in Norwegian. (That was so embarrassing- det var så pinlig). And embarrassed would be translated to flau. (I was so embarrassed- jet var så flau). The difference is if one is talking about a situation, or how one felt during the situation. But it’s likely that slang has different meaning in different areas in a country, so maybe in Oslo, klein means embarrassing. (Thank you to @helena1205 for this edit)

konse: verb, (infinitive- å konse), to concentrate.

kos: noun, cosyness, (hygge).

kred: noun, street cred, taken from English.

kødde: verb, to kid/ take the piss, “kødder du meg”.

NKVO: slang, “Nå koser vi oss”, now we are going to enjoy ourselves/ now we are enjoying ourselves.

Olafiaklinikken: noun, a clinic in Oslo where one can get free gynecological/ urological tests.

seff: a saying, of course. Short for “selvfølgelig“.

serr: a saying, seriously?. Short for “seriøst”.

snill: adjective, kind.

I hope this is useful/ accurate! This post is supported by a post in Kosegruppa DK, I just translated it into English so you guys can have some extra help learning Norwegian words.