pip vs gun down

pip is a noun but gun down is not a noun.

Word	Noun	Adjective	Verb	Adverb
pip	Yes	No	Yes	No
gun down	No	No	Yes	No

As verbs, gun down is a hyponym of pip; that is, gun down is a word with a more specific, narrower meaning than pip:

Other hyponyms of pip include grass, kneecap.

pip (noun)	gun down (noun)
a mark on a die or on a playing card (shape depending on the suit)
a radar echo displayed so as to show the position of a reflecting surface
a small hard seed found in some fruits
a disease of poultry
a minor nonspecific ailment

pip (verb)	gun down (verb)
defeat thoroughly	strike down or shoot down
hit with a missile from a weapon
kill by firing a missile