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.
benefactor
The definition for benefactor is "One who offers financial help." Used in a sentence: Michael's aunt and benefactor paid his college tuition.
ethical
The definition for ethical is "Conforming to accepted standards." Used in a sentence: Mary did the ethical thing and turned in the diamond necklace she found.
redouble
The definition for redouble is "To make twice as great." Used in a sentence: As the sun began to set, Brittany redoubled her effort to find the necklace she had dropped in the field.
untenable
The definition for untenable is "Not able to be defended." Used in a sentence: Rashid made the untenable statement that George Washington was the second president of the United States.