The definition for appraise is "To evaluate the worth of." Used in a sentence: Simone, an expert in African sculpture, was asked to appraise the ambassador's collection of masks.

The definition for diffident is "Lacking self–confidence." Used in a sentence: The diffident student never raised her hand in class, even when she knew the answer.

The definition for incumbent is "Necessary as a duty or responsibility." Used in a sentence: It was incumbent on Jack to attend his father's retirement party.

The definition for melee is "A tumultuous fight among several people." Used in a sentence: After the game, a melee broke out between fans of the opposing teams.

The definition for regurgitate is "To pour out or throw back." Used in a sentence: The teacher wanted us to examine ideas rather than to regurgitate memorized facts.