gargantuan
The definition for gargantuan is "Gigantic." Used in a sentence: The gargantuan monster towered over the ten–story bulding.
garish
The definition for garish is "Offensively bright." Used in a sentence: The garish wallpaper offended Jerome, who preferred subtle colors.
negate
The definition for negate is "To make invalid." Used in a sentence: Paula negated Tiffany's argument by proving that her main premise was false.
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.
polarize
The definition for polarize is "To break up into opposing groups." Used in a sentence: Thelma tended to polarize discussions rather than to encourage compromise.