To be used when referring to the sentience of a being or normally non-sentient object e.g. Herbie ('The Love Bug') is a sentient car.
Sentience is the ability to have sensations or experiences; a creature, machine, or thing with the ability to feel, perceive, be aware of their surroundings and/or effects upon their person or environment, and not necessarily react in a perceivable algorithmic manner is said to be sentient.
In our context, often this tag is used for non-organically-humanoid beings that react like beings similar to humans. Robots, advanced dolphins, nanobot-arrays, and entire stars have applied to this status in sci-fi.