Kamasutra 2.3.20

2.3.20

oṣṭhasaṃdaṃśenāvagṛhyauṣṭhadvayam api cumbeta/ iti saṃpuṭakaṃ striyāḥ, puṃso vā +ajātavyañ janasya//

When one of them takes both the lips of the other between his or her own, it is called "a clasping kiss." A woman, however, only takes this kind of kiss from a man who has no moustache. And on the occasion of this kiss, if one of them touches the teeth, the tongue, and the palate of the other, with his or her tongue, it is called the "fighting of the tongue." In the same way, the pressing of the teeth of the one against the mouth of the other is to be practiced.