fickle
The definition for fickle is "Lacking constancy, changeable." Used in a sentence: The fickle Senji had a new best friend every month.
incidental
The definition for incidental is "Minor." Used in a sentence: The accountant advised Justine not to report her incidental expenses.
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.
melee
The definition for melee is "A tumultuous fight among several people." Used in a sentence: After the game, a melee broke out between fans of the opposing teams.
recrimination
The definition for recrimination is "A retaliatory accusation." Used in a sentence: Frank, who was wounded by Sally's remark, made a bitter recrimination.