The definition for authoritarian is "Favoring absolute obedience to authority." Used in a sentence: Marco's authoritarian mother never allowed him to watch more than one hour of television a day.

The definition for commemorate is "To mark by a ceremony." Used in a sentence: Each year, the Franklins commemorate their anniversary by visiting the site of their first date.

The definition for disconcert is "To throw into confusion." Used in a sentence: Jennifer's outspoken criticism of the meal disoncerted the waiter.

The definition for iridescent is "Having a lustrous or attractivve quality." Used in a sentence: The movie star's iridescent presence charmed even the hardened reporter.

The definition for placebo is "An inactive substance used in medical testing." Used in a sentence: Tom, who had taken the placebo, found that his allergy symptoms did not go away.