left-handed pitcher vs lefty

left-handed pitcher and lefty both are nouns.

Word	Noun	Adjective	Verb	Adverb
left-handed pitcher	Yes	No	No	No
lefty	Yes	No	No	No

As nouns, left-handed pitcher and lefty are synonyms defined as:

left-handed pitcher and lefty: a baseball pitcher who throws the ball with the left hand

Other synonyms of left-handed pitcher include left-hander, left hander, lefthander, southpaw.

left-handed pitcher (noun)	lefty (noun)
a baseball pitcher who throws the ball with the left hand	a person who uses the left hand with greater skill than the right
	a baseball pitcher who throws the ball with the left hand