Under the tongue (sublingual) is one method of administration of different drugs.

You can buy or make tinctures with ethanol. By holding the liquid under the tongue, the THC and other cannabinoids enter the bloodstream faster and more efficiently than going through the digestive tract. The high may last longer than smoking, but shorter than eating. It can take an hour or more to feel effects from eating, as opposed to maybe 15 minutes for the tincture.