adversary
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.
beneficial
The definition for beneficial is "Helpful." Used in a sentence: there is no doubt that eating vegetables is beneficial to one's health.
epistolary
The definition for epistolary is "Contained or carried on in letters." Used in a sentence: The shoebox filled with letters was the ony remains of Ming's epistolary friendship with Emile.
incongruous
The definition for incongruous is "Not harmonious, incompatible." Used in a sentence: Sadie's cowboy hat was incongruous with her black cocktail dress.
iridescent
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.