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2.
A smile of crooked, stained, yellow teeth; originating from the stereotype of Brits having bad teeth
American: Hey hey hey, Brit.

Englishman: 'Ello, love. *grins*

American: You know, I think I know the perfect dentist to take care of that British smile of your's.
by strippapole13 December 23, 2011
 
1.
any smile exhibiting bad teeth, characterized by poor orthodontia, caries, and other dental maladies stereotypically associated with the British, but actually observed in all peoples globally.
The authenticity of english spy character, austin powers, was sacrificed in the movie sequel when he lost his british smile.
by T. Emerson Coleman November 24, 2007
 
3.
a term mainly used by african parents to their children. This is where someone is smiling or laughing without meaning it.
one friend says a really unfunny joke

the other puts on a british smile and pretends to find it funny
by baddog64 May 11, 2009