pigeon breast vs deformity

pigeon breast and deformity both are nouns.

Word	Noun	Adjective	Verb	Adverb
pigeon breast	Yes	No	No	No
deformity	Yes	No	No	No

As nouns, deformity is a hypernym of pigeon breast; that is, deformity is a word with a broader meaning than pigeon breast:

pigeon breast: abnormal protrusion of the breastbone caused by rickets
deformity: an affliction in which some part of the body is misshapen or malformed

Other hypernyms of pigeon breast include malformation, misshapenness.

pigeon breast (noun)	deformity (noun)
abnormal protrusion of the breastbone caused by rickets	an appearance that has been spoiled or is misshapen
	an affliction in which some part of the body is misshapen or malformed