The definition for combustion is "Act of burning." Used in a sentence: Campers must use fire with great caution to prevent combustion of the parched brush.

The definition for corroborate is "To support with evidence." Used in a sentence: "Unless you can corroborate your story, it will not be admissible in court," the attorney told his client.

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 eulogy is "Speech or writing in praise of deceased." Used in a sentence: Ernesto delivered a moving eulogy at his uncle's funeral.

The definition for gruff is "Rough or stern in manner or speech." Used in a sentence: Heidi's grandfather was gruff, barking stern orders and hardly smiling.