{i} sending an employee from his/her regular office/post for temporary assignment somewhere else; (British) transfer of a military officer to another post for temporary duty; indorsement, speech seconding a motion, support for a proposal or statement
Someone who is on secondment from their normal employer has been sent somewhere else temporarily in order to do special duties. We have two full-time secretaries, one of whom is on secondment from the Royal Navy. a period of time that you spend away from your usual job, either doing another job or studying on secondment (from sth)
New functions given to employees for a temporary period at the same level Employees resume their former duties at the end of the secondment The term refers to an assignment between departments and requires a written agreement