door guard vs doorkeeper

door guard and doorkeeper both are nouns.

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

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

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

door guard (noun)	doorkeeper (noun)
someone who guards an entrance	someone who guards an entrance
	an official stationed at the entrance of a courtroom or legislative chamber
	the lowest of the minor Holy Orders in the unreformed Western Church but now suppressed by the Roman Catholic Church