oblivious
The definition for oblivious is "Lacking awareness." Used in a sentence: Love–struck Charlie was oblivious to everyone but the object of his affection.
plaudits
The definition for plaudits is "Enthusiastic approval." Used in a sentence: Allison's painting met with plaudits from the critics, who had dismissed her earlier work.
revive
The definition for revive is "To bring back to life." Used in a sentence: Hank tried to revive Clare's interest in the project, but her enthusiasm had expired.
stern
The definition for stern is "Harsh, severe." Used in a sentence: The stern principal canceled the prom after the seniors played a silly prank.
unscrupulous
The definition for unscrupulous is "Lacking principles." Used in a sentence: The unscrupulous salesman was fired for lying to his customers.