2 definition by djkt

Half gaff is defined in the Scottish slang folklore as a party with not enough people to call it a full party. For example a 'party' with under 20 people would be defined as a 'half gaff'.
'Thought it was going to be a full on party last night man?'
'Nah not enough people had to be a half gaff bro.'

'Man we was having a hella good night then Marvin pulls out his phone and starts sexting his boss'
'Dammit Marvin! He be always doing the Dougie on nights out!'