K
- Karno's Army
- a chaotic, ineffective team (usually: Fred Karno's Army) (related US: Keystone Kops, Gang That Couldn't Shoot Straight)
- kecks
- (informal, also spelt keks) trousers or underpants
- kerfuffle *
- a disorderly outburst, disturbance or tumult; from Scots carfuffle
- kazi
- (slang) lavatory (numerous alternative spellings are seen, such as karzy, karsey, carzey etc.)
- kip
- (slang) sleep. (US and UK: nap)
- kit
- (slang) clothing: hence "Get your kit off": an exhortation to get undressed
- kitchen roll
- paper towels
- knackered
- (slang) exhausted, originally 'sexually exhausted', derived from an old use of the verb meaning 'to castrate'
- knacker's yard
- premises where superannuated livestock are sent for rendering, etc. (glue factory). Sometimes refers to the same for vehicles, a scrapyard (US: junkyard)
- knackers
- (slang) testicles
- knickers
- girls' and women's underpants (US: panties): hence, "Don't get your knickers in a twist" (US: don't get your panties in a wad, keep calm, hold your horses, chill out)
Read more about this topic: List Of British Words Not Widely Used In The United States