chair warmer

noun Informal.

an officeholder, employee, or the like, who accomplishes little, especially a person who holds an interim position.
a person who lounges for long periods sitting in a chair, as in a hotel lobby or clubroom.

Origin of chair warmer

First recorded in 1905–10

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018