Derogatory, comes from the name of a British skip company, a 'biffa' is a fat person.
Describing something as biffing is like describing something as huge.

Someone who has sex against or in a bin on a night out while intoxicated

one dreadfully looking young lady, usually overweight, spotty and easy...

biffa-meaning fat or stupid
other meaning or sayings around the word biffa-chiffa meaning chubby biffa or biffaish meaning if somthing is not very fat but abit fat.

A style of management, ie rubbish, based on the waste disposal company in Britain of that name

A commonly used insult from a man to an extremely ugly/unatractive girl.

Mostly used on drunken nights out!

A short and to the point definition of someone who has an unattractive personality and/or is ugly,

or/and

think they are or think they are perceived to be very good looking.
or/and

a person who is both not a very nice person and painful to look at.