To set fire to ones flatulent gassy fart. Can be done alone or as a party piece. If done with a crowd of mates a competitive element may arise to see who can burn off the longest flame.
"Quick, Lend me your lighter" said Andrew, "I've been on the baked beans, sprouts and Guinness again so stand well back while I burn one off".
went to an indian restaurant last night to have a mildcurry and it turned out to be a burn your face off curry had a beer and 2 litres of milk to cool me down.