Means impressively big, strong, or just properly great. You’ll hear it in stuff like stonking great, stonking big, or stonking good. It’s a slightly daft, old-school Brit word that somehow makes the exaggeration feel even more legit. Perfect for portions, bonuses, hangovers, or anything that’s gone absolutely massive.
"Dave rocked up with a stonking great fry-up, proper builder’s breakfast. I said steady on, mate, you feeding a family of badgers or what?"