The definition for adversary is "One who opposes or resists." Used in a sentence: Franklin hoped to defeat his adversary in the afternoon's tennis match.

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 dubious is "Questionable." Used in a sentence: Karl found Kevin's claim that he was sick dubious, as he had just seen him playing football.

The definition for redouble is "To make twice as great." Used in a sentence: As the sun began to set, Brittany redoubled her effort to find the necklace she had dropped in the field.

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.