stupid person vs pillock

stupid person and pillock both are nouns.

Word	Noun	Adjective	Verb	Adverb
stupid person	Yes	No	No	No
pillock	Yes	No	No	No

As nouns, stupid person and pillock are synonyms defined as:

Other synonyms of stupid person include dolt, dullard, poor fish, pudden-head, pudding head, stupe, stupid.

stupid person (noun)	pillock (noun)
a person who is not very bright	a person who is not very bright