Slangs are the expressions which are used in their most informal usages.Slang is language at its most informal, using expressions that many would consider to be grammatically imperfect and sometimes rude. Slang often used within small social groups where it can help draw and keep the group together. It changes very quickly in English.
Cockney Rhyming Slangs are the specialised forms of slangs used in the East of London. This kind of Slang is a kind of antilanguage where words are replaced by phrases that rhyme (sound the same): North and south = mouth Adam and Eve = believe Sometimes, the last word is dropped.
Slangs beginning with J :
Jab : (UK) A jab is an injection, both medical and non-medical.
Jabber : If someone jabbers, they talk a lot but don't make any sense, usually because they are excited, scared, etc.
Jack : To jack is to steal. (from Hijack)
Jack : (USA) Jack is money.
Jacked : If something is jacked, it is stolen. (It comes from 'hijacked'.)
Jacko : A jacko is a slang term for a paedophile (pedophile)- someone who molests children sexually.
Jackson : (USA) A Jackson is a twenty dollar bill.
Jammy : (UK) Someone who is jammy is very lucky, especially when their luck is undeserved.
Jawache :(UK) To jawache is to kiss someone.
Joanie : (USA) If something is Joanie, it's old-fashioned.
Job : (UK) A job is a crime.
Jobsworth : (UK) A jobsworth is an annoying official who sticks to rules no matter how petty or trivial they are. (It comes from 'more than my job's worth', which means they think any deviation would place their job at risk.)
Jock : (USA) A jock is an athlete, especially in colleges or universities.
John : (USA) The john is the bathroom or toilet.
Johnson : (USA) This is a term for the penis.
Joint : 'Joint' is a term for a cannabis cigarette.
Jordan : (USA) A jordan is an attractive male.
Jugs : Jugs are a woman's breasts, especially if they are large.
Juk : (UK) To juk someone is to stab them.
Jumper : (UK) A jumper is a thief who steals from offices.
Junkie : A junkie is a heroin addict, though the term is often used for drug addiction.