derived from playstation gaming. Used when one player has tried to describe a complex move by just saying that he pressed square triangle (the square button then the triangle one). More universally, it's used when someone states the most bloody obvious option for solving a complex problem, an option that the person has of course already tried.
'Have you seen my gloves?'
'Are they in the glove compartment?
'SquareTriangle.'
The noise made and unsatisfactory delivery of the contents of a squeezy bottle sauce if it has not been stored correctly, vertically on its cap. Etymology squirt and fart.
The squarting ketchup prompted aunt Nelly to hurriedly open the windows during last Fridays dinner party