Unparliamentary language is language that breaks the rules of politeness in the House of Commons Chamber. Part of the Speaker's role is to ensure that MPs do not use insulting or rude language and do not accuse each other of lying, being drunk or misrepresent each other's words. Words to which objection has been taken by the Speaker over the years include blackguard, coward, git, guttersnipe, hooligan, rat, swine, stoolpigeon and traitor. The Speaker will direct an MP who has used unparliamentary language to withdraw it. Refusal to withdraw a comment might lead to an MP being disciplined. MPs sometimes use considerable ingenuity to get around the rules; for example Winston Churchill famously used the phrase "terminological inexactitude" to mean "lie".
contributed by user local yokel