What is the meaning of the furniture term Grandfathers Clock?

The term Grandfathers Clock refers to a tall, free-standing pendulum clock that typically reaches the height of a grandfather or tall standing figure. It is also known as a longcase clock or a tall-case clock. These clocks consist of a long, narrow case that usually houses the pendulum and weights, along with a face displaying the time and other clock mechanisms. The name Grandfathers Clock originates from the popular song My Grandfathers Clock by Henry Clay Work, which celebrated such timepieces. Tall clock case.