piercing vs penetrating

piercing and penetrating both are adjectives.

Word	Noun	Adjective	Verb	Adverb
piercing	No	Yes	No	No
penetrating	No	Yes	No	No

As adjectives, piercing and penetrating are synonyms defined as:

piercing and penetrating: having or demonstrating ability to recognize or draw fine distinctions

Other synonyms of piercing include acute, discriminating, incisive, keen, knifelike, penetrative, sharp.

piercing (adjective)	penetrating (adjective)
having or demonstrating ability to recognize or draw fine distinctions	having or demonstrating ability to recognize or draw fine distinctions
painful as if caused by a sharp instrument	tending to penetrate; having the power of entering or piercing