Other forms: linguals
Something that's lingual has something to do with tongues — it's near a tongue, looks like a tongue, or is caused by a tongue. The lingual side of your teeth is the side closest to your tongue.
If you fall and bite your tongue, you suffer a lingual injury, and when you brush your tongue after finishing with your teeth, you could call it a lingual cleaning. Because speech sounds are formed with the help of the tongue, things related to language are also lingual. A skilled lingual learner is good at picking up languages, for example. The Latin root, lingua, unsurprisingly, means "tongue."