To breakwind or fart. (ie. to emit wind from the anus, squeeze cheese, float an air biscuit, a bottom
burp, flatulate, etc, etc).
Bloff is a contraction of "Blow off" (which is an English term for farting (not to be confused with the American term "Blow off" which is
unrelated).
Sometimes there is not an inoffensive or child-safe word for flatulence in polite company, this is where bloffing comes in. To say someone is bloffing is
far more socially acceptable, and even child
friendly. It's especially easy to tell your kid to stop bloffing in a crowded restaurant, for example. Equally, it's not a big issue if your child shouts out "I did a bloff" in a supermarket or such!