an individual, in civil proceedings, assigned to maintain assets of an organization; for example, in a lawsuit between shareholders, a judge may be asked to replace an executive who holds shares with a retainer if they believe there is a danger of the executive running the company into the ground

a person being part of the retinue (suite, train) of a dignitary etcetera, either performing personal services such as man servant, pageboy, bodyguard, or rather occasionally in proximity such as a minstrel

A retainer agreement is a contract between two people or companies where one pays to reserve the other's time. The agreement includes the salary to be paid, the period of time to be reserved (for instance, one week per month), and details on the type and scope of work to be done by person or company under retainer. Often included are also specific goals, called milestones, to be accomplished within a certain period of time.

RFA Retainer (A329), an armament support ship

a vassal in feudal Japan, often Samurai providing military services

the part of a contractually due sum that is paid in advance, while the balance will only follow after receipt on the counterpart in goods or services; also called advance payment or deposit

a device in dentistry: Retainer (orthodontic device) used to correct or keep teeth corrected