Means to splash out and spend more than you normally would, usually because it’s a special occasion. Think posh meal, extra rounds, nicer hotel, the full works. It’s not just spending, it’s making a proper gesture and being a bit generous with it. Honestly, a top-tier phrase for justified financial chaos.
"It’s your promotion, so we’re pushing the boat out. No sad Tesco meal deal tonight, we’re off for a proper curry and a couple of pints, yeah?"