One of the mysteries of the English language finally explained.
Definition of British Bulldog in English:
British Bulldog
noun
1The bulldog, regarded as a quintessentially British breed and used to symbolize a spirit of courage and tenacity thought characteristic of the British; (hence) a courageous or tenacious British person.
2A children's game in which players have to cross an open space without being intercepted and seized by an opponent in the middle, those caught joining the opponent in attempting to catch other players.
Origin
Early 19th century; earliest use found in Bristol Mercury.