Rider slang for a pinch flat: the tube gets crushed between rim and edge and tears. It needs a tube — on a tubeless setup it cannot happen at all.
Tyre pressure is the cheapest grip lever you have — and a snakebite marks the lower limit. If the tyre collapses too far over an edge or a rock, the rim crushes the tube against the ground and it tears. The typical error runs both ways: plenty of riders carry road-bike pressure onto gravel or a trail and lose grip, while others panic-inflate rock hard after a flat and lose it just the same. Instead, work down in steps of 0.1 to 0.2 bar until the tyre rolls settled but the rim no longer bottoms out. What often goes unnoticed: without a tube a snakebite is impossible, but a hard rim strike is not — tubeless is no licence for arbitrarily low pressure, and a spare tube still belongs in your saddle bag.