Definition of "retainer"

retainer

/ɹɪˈteɪn.ə/

noun
plural retainers
1. Any thing or person that retains.
2. A dependent or follower of someone of rank.
  Quotations
  If they possessed the means to marshal labour, pile up food resources and provender armies of year-round retainers, what sort of royalty would consciously elect not to do so.
  2021 October 19, David Graeber, David Wengrowr, “Unfreezing the ice age: the truth about humanity’s deep past”, in The Guardian, UK
3. A paid servant, especially one who has been employed for many years.
4. A fee one pays to reserve the other's time for services.
5. (dentistry) A device that holds teeth in position after orthodontic treatment.
  Quotations
  You give me head / It makes it worse / Take out your fuckin' retainer / Put it in your purse
  1981, “Too Drunk to Fuck”, performed by Dead Kennedys
6. (rail transport, mechanical engineering) A retaining valve.