hash. Hash (hashish) is the resin collected from the flowers of the cannabis plant. The primary active substance is THC (tetrahydrocannabinol) although several other cannabinoids are known to occur. Hash is usually smoked in pipes, water pipes, joints, and hookahs, sometimes mixed with cannabis flowers or tobacco.ontrary to popular belief, the effects from smoking cannabis or hash are not increased by holding the smoke in the lungs longer. Almost all of the THC is absorbed within the first few seconds. Also contrary to popular belief, more potent cannabis or hash is not more dangerous.