When a joint or blunt canoes, it's burning unevenly. If it burns down one side and not the other, it resembles a canoe, with one side hollowed out and the other, unburnt side still intact (like a hull). Canoeing is a problem because it means that a lot of the cannabis in the joint or blunt is un-smoked and might be wasted if you can't find something to put it in. It also means the joint might fall apart completely. If your joint starts to canoe, try licking your finger and applying a small amount of saliva to the side that's burning (effectively putting out the fire).
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