avian
The definition for avian is "Relating to birds." Used in a sentence: The old man affectionately referred to pigeons as his "avian friends."
illuminate
The definition for illuminate is "To make clear." Used in a sentence: Her excellent lecture illuminated the complicated subject of nuclear physics.
opportune
The definition for opportune is "Suitable or convenient." Used in a sentence: Quan stepped onto the platform at the most opportune time, just as the train pulled in.
surplus
The definition for surplus is "Excess." Used in a sentence: Trevor decided to freeze the surplus chili for next week's tailgate party.
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.