door guard vs doorman

door guard and doorman both are nouns.

Word	Noun	Adjective	Verb	Adverb
door guard	Yes	No	No	No
doorman	Yes	No	No	No

As nouns, door guard and doorman are synonyms defined as:

Other synonyms of door guard include doorkeeper, gatekeeper, hall porter, ostiary, porter.

door guard (noun)	doorman (noun)
someone who guards an entrance	someone who guards an entrance