Refers to the physical tip of the tongue. Common in expressions like 舌先で舐める (lick with the tip of the tongue) or 舌先がしびれる (the tip of the tongue feels numb).
I burned the tip of my tongue on the hot soup.
He licked his lips with the tip of his tongue.
glib tongue; smooth talk; deceptive eloquence
smooth talk; glib tongue; flattery designed to deceive
Compound of 舌 (tongue) and 先 (tip, end).