/ rɪˈteɪnə(r); NAmE / noun
1.
a sum of money that is paid to sb to make sure they will be available to do work when they are needed :
The agency will pay you a monthly retainer.
2.
( BrE ) a small amount of rent that you pay for a room, etc. when you are not there in order to keep it available for your use
3.
( NAmE ) a device that keeps a person's teeth straight after they have had orthodontic treatment with a brace
4.
( old-fashioned ) a servant, especially one who has been with a family for a long time