house dick vs private detective

house dick and private detective both are nouns.

Word	Noun	Adjective	Verb	Adverb
house dick	Yes	No	No	No
private detective	Yes	No	No	No

As nouns, private detective is a hypernym of house dick; that is, private detective is a word with a broader meaning than house dick:

house dick: a private detective employed by a hotel or retail store
private detective: someone who can be employed as a detective to collect information and assist in criminal investigations

Other hypernyms of house dick include operative, PI, private eye, private investigator, shamus, sherlock.

house dick (noun)	private detective (noun)
a private detective employed by a hotel or retail store	someone who can be employed as a detective to collect information and assist in criminal investigations