Which of the following best defines a cliche?

A cliche refers to an idea or expression that has become so overused that it has lost its original impact or novelty. The essence of a cliche lies in its frequent use, which causes it to become dull and uninspiring, often failing to evoke the intended response from an audience. This is why the definition that describes a worn-out idea or overused expression is the most accurate.

In contrast, the other options describe concepts that are fundamentally different: an innovative idea or expression denotes freshness and originality; a striking metaphor holds creative and vivid imagery that captures attention; and a profound insight implies a deep understanding or significant revelation. None of these relate to the repetitive and unoriginal nature of a cliche.