提供一份挑战性的GRE词汇列表，包括单词、定义和用法示例。
以下是一个挑战性的GRE词汇列表，包括单词、定义和用法示例：

1. ubiquitous - (adj.) present or found everywhere
   Example: The internet has become ubiquitous in modern society.

2. panacea - (n.) a supposedly universal remedy
   Example: Some people believe that exercise is a panacea for all health problems.

3. ephemeral - (adj.) short-lived, temporary
   Example: The beauty of the cherry blossoms is ephemeral; they only bloom for a few weeks each year.

4. harangue - (n.) a long, passionate, and aggressive speech
   Example: The politician's harangue lasted for over an hour, but failed to persuade many listeners.

5. capricious - (adj.) prone to sudden and unpredictable changes of mood or behavior
   Example: You never know what to expect with her; her moods are very capricious.

6. fastidious - (adj.) very attentive to detail, meticulous
   Example: She was fastidious about every aspect of her work, from the smallest details to the big picture.

7. sagacious - (adj.) wise, shrewd, displaying good judgment
   Example: His sagacious advice helped us avoid a costly mistake.

8. mellifluous - (adj.) sweetly or smoothly flowing, pleasant to the ear
   Example: The singer's mellifluous voice captivated the audience.

9. obfuscate - (v.) to make something unclear or confusing, to obscure
   Example: The lawyer obfuscated the truth in order to win the case.

10. laconic - (adj.) using very few words, concise to the point of being rude
    Example: His laconic response to my question left me frustrated and unsatisfied.