In a sentence
The discovery threatened to upend decades of accepted theory.
Synonyms
overturntoppleupset
Antonyms
preservemaintainstabilize
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See all More GRE words starting with U
ubiquitous
seeming to be present everywhere at the same time
ululate
to howl or wail loudly, especially in grief or celebration
umbrage
offense or annoyance taken at a perceived slight
unalloyed
complete and unqualified, without anything to diminish it
unanimity
complete agreement among everyone involved
unassailable
impossible to attack, question, or refute
unassailed
not subjected to attack or challenge
unassuming
modest and not seeking to draw attention to oneself
Learn words the way the GRE tests them.
Vocabulary sticks when you meet it in real sentences. Practise these words inside text completion and sentence equivalence questions.