Liquid THC is a tincture of tetrahydrocannabinol, one of the main psychoactive chemicals in marijuana. Liquid THC can be heated and vaporized to produce effects on the body similar to smoking dried marijuana buds and leaves.
A tincture is a way of preparing a drug such that the active ingredient is extracted into a liquid solvent, especially alcohol. Tinctures usually involve plant extracts, though sometimes animal extracts or even minerals such as iodine are prepared in this way.
Liquid THC tinctures for oral use may use alcohol, vinegar or glycerol as the solvents. THC can also be dissolved in oil, which is the more common liquid solvent used in vaporizers. Typically, liquid THC is consumed by placing several drops below the tongue via an eye dropper. It can also be loaded into a vaporizer and heated; this method is very similar to smoking it.
As of 2015, all forms of marijuana, including THC, are considered illegal by the U.S. federal government, although certain states allow its use.