door guard vs ostiary

door guard and ostiary both are nouns.

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

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

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

door guard (noun)	ostiary (noun)
someone who guards an entrance	someone who guards an entrance
	the lowest of the minor Holy Orders in the unreformed Western Church but now suppressed by the Roman Catholic Church