In Britain [& I guess other places too] there's many words & expressions in commonplace use which don't appear in most dictionaries,

These terms aren't neccessarily slang, but perhaps more to do with area or dialect.

As well as being present in everyday speech in many places, this language also appears in folk [type] songs.


One which springs to mind is such as 'Whisht lads, ard ye gobs' [Lambton Worm] 'gob' meaning 'mouth'

More?