when you're jacking off and you're not really feeling it yet but you cum anyways and you end up feeling horny again soon thereafter. usually happens when you're in a rush or about to get caught.
i was wacking it to some hot pics of jenna juggs 'til i heard someone knocking and i half-gasmed. total buzzkill.
half gaff is a Scottish term used to describe a party that has a smaller number of people than a usual one.
Half gaff is defined in the Scottish slangfolklore 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.'