Below are a list of words that are strictly used in British English (not in the US), they are all colloquial words which are commonly used in informal situations. Some of them are slang.After you have read the words, their synonyms and examples you should check them again on this online dictionary which has an audio function to help you with pronunciation.
1.) Knackered (adjective)
Really tired, exhausted.
"I'd love to go out tonight but I'm knackered, I'm sorry, I'll have to give it a miss."
"You look knackered, you should go home and get some sleep."
2.) Dodgy (adjective)
false, dishonest, causing a lack of trust.
"The email said that if I send them my bank details they will send me money."
"That sounds dodgy to me, there's a lot of scams going round on the Internet, you should be careful."
"I think it's a pretty safe area during the day but I've heard it's a bit dodgy at night."
"Are you sure you want to meet him on your own, he looks dodgy, I don't trust him."
3.) Whinge ( verb)
to complain continuously in an irritating way, moan, whine.
"Stop whinging and get on with it!".
"If you want anything done in this country, you've got to whinge till you're blue in the face!"
4.) Stroppy (adjective)
bad tempered, easily annoyed, touchy, belligerent.
"There's no need to get stroppy with me!".
"She's acting like a stroppy teenager again."
5.) Peckish (adjective)
somewhat hungry, to have an appetite.
"If you're feeling a bit peckish, there's plenty of fruit."
"Oh no, I couldn't eat a pizza, I'm just peckish, a sandwich will do."
6.) Chuffed (adjective)
quite pleased, delighted.
"I passed my driving test, I'm well chuffed."
7.) Gobsmacked (adjective)
astonished, really surprised, shocked.
"I was gobsmacked when I found out it was him, I always thought he was such a nice man."
"She was gobsmacked when I asked her to marry me, I'm still waiting for her answer!"
8.) Shambles (adjective)
a total mess, disorganised, complete disorder.
"The economy is in a shambles."
"It is possible to cook the dinner and not leave the kitchen in a shambles, you're not the only one who lives here, you know."
9.) Blatant (adjective)
Obvious, clear for everyone to see, offensively noticeable.
"That is a blatant lie."
"I can't believe he did that, what a blatant disregard for her feelings!"
10.) Shirty (adjective)
"Don't get all shirty with me!"
"He was a bit shirty with her when she arrived late".
If you would like to learn more British slang have a look at the top 100 most beautiful British slang words and phrases