corroborate
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.
incumbent
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.
obnoxious
The definition for obnoxious is "Highly offensive." Used in a sentence: The manager asked the obnoxious diner to leave the restaurant.
pretentious
The definition for pretentious is "Making unjustified claims." Used in a sentence: The pretentious boy said that he was the fastest runner, but he finished last in the race.
unscrupulous
The definition for unscrupulous is "Lacking principles." Used in a sentence: The unscrupulous salesman was fired for lying to his customers.