Time for some more British slang.
Morish - Also spelt "moreish", this word is used to describe desserts in my house, when a single helping is simply not enough. You need more! It applies to anything - not just desserts.
Mufti - An old army term for your "civvies". Civilian clothes that is, rather than your uniform.
Mug - If someone is a bit of a mug, it means they are gullible. Most used car salesmen rely on a mug to show up so they can sell something!
Mush - Rhymes with "push". Slang word for your mouth as in "shut your mush". Also means mate as in "Alright mush?. Which means "Hi"!
Mutt's nuts - If something is described as being "the Mutt's" then you'll know it is fantastic or excellent. "The Mutt's" is short for "The Mutt's nuts" which is clearly another way of saying the "Dog's Bollocks"! All clear now?
Naff - If something is naff, it is basically uncool. Anoraks are naff, salad cream is also naff. You could also use it to tell someone to naff off, which is a politer way of telling them to f*** off!
Nancy boy - If someone is being pathetic you would call them a nancy or a nancy boy. It is the opposite of being hard. For example in cold weather a nancy boy would dress up in a coat, hat, gloves and scarf and a hard guy would wear a t-shirt. It's also another word for a gay man.
Nark - If someone is in a nark, it means they are in a bad mood, or being grumpy. It's also the word for a spy or informant. For example a coppers nark is someone who is a police informant - which you might call a stoolie or stool-pigeon. The origin is from the Romany word, nak, meaning "nose".
Narked - In the UK you would say that someone looked narked if you thought they were in a bad mood. In the US you might say that someone was pissed. We definitely would not say that, as it would mean they were drunk!
Nesh - My Dad used to call me a nesh wimp when I was a kid and I wanted him to take me places in his car because it was too cold to go on my bike. He meant I was being pathetic or a bit of a nancy boy. He might have had a point!
Nice one! - If someone does something particularly impressive you might say "nice one"! to them. It is close the Texan good job that you hear all the time.
Nick - To nick is to steal. If you nick something you might well get nicked.
Nicked - Something that has been stolen has been nicked. Also, when a copper catches a burglar red handed he might say "you've been nicked"!
Nitwit - See twit.
Nookie - Nookie is the same as hanky panky. Something you do with your bird!
Nosh - Food. You would refer to food as nosh or you might be going out for a good nosh up, or meal! Either way if someone has just cooked you some nosh you might want to call it something else as it is not the nicest word to describe it.
Not my cup of tea - This is a common saying that means something is not to your liking. For example if someone asked you if you would like to go to an all night rave, they would know exactly what you meant if you told them it was not exactly your cup of tea!
Nowt - This is Yorkshire for nothing. Similarly owt is Yorkshire for anything. Hence the expression "you don't get owt for nowt". Roughly translated as "you never get anything for nothing" or "there's no such thing as a free lunch".
Nut - To nut someone is to head butt them. Nutting is particularly useful when at a football match.
Off colour - If someone said you were off colour they would mean that you look pale and ill! Not quite the same as something being off colour in the US!
Off your trolley - If someone tells you that you're off your trolley, it means you have gone raving bonkers, crazy, mad!
On about - What are you on about? That's something you may well hear when visiting the UK. It means what are you talking about?
Clancy's comment: Right you are, Governor. I'm off to get some nosh.