Can't see the other tip side - past the threaded.
So it looks to be on a harness - noted the Braided sheath to protect it either from abrasion or hot parts.
Seeing how it's not "ventilated" like what an O2 sensor would need - can only presume it is a temperature sure sensor of some kind, dealing with water/coolant or air intake.
Seeing the powdery - thinking it's coolant temp