When people smoke a lot of weed/cannabis/marijuana and smokers get a physical high and their legs feel really heavy. Often they want to get up realize they have stoner legs and just zone out sitting down for a bit.
John: "Why has Martin been sitting on the couch for 3 hours without getting up?"
Bob: "I reckon he's got a bad case of stoner legs, he keeps looking up at the ceiling.."
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