This is a colloquial term from Coleraine, County Londonderry, Northern Ireland.
The phrase refers to a method of laughter; the perpetrator unveils the joke and proceeds to slap their leg. Simultaneously, the perpetrator adopts an inhuman grin, projects a dry hoarse laugh and scans the room with piercing, desperate eyes with the intention to induce laughter from at least one sympathetic person.
If the attempt is unsuccessful, the perpetrator must proceed to insult someone to cover up their failure.
Victims: ''Naw man''
Perpetrator: ''Well I'd shag Lyndsay Taggart''
Victims: ''Don't try to pull a Loughrey''