stealing someone's thunder

Verb

steal someone's thunder (third-person singular simple present steals someone's thunder, present participle stealing someone's thunder, simple past stole someone's thunder, past participle stolen someone's thunder)

1. (idiomatic) To appropriate someone's ideas or information, typically in order to look better at that person's expense.
   • There are several upstarts, who, without the genius to invent a style, have been copying yours, and trying to steal your thunder.1855, Jno. E. Vought, “Editor's Table (letters)”, in The Knickerbocker: Or, New-York Monthly Magazine Volume 46, page 101
2. (idiomatic) To detract from someone's accomplishments or glory; to undermine.
   • Can Your Competition Steal Your Thunder? Make sure that your competitors can't undermine your statement.2005, Walter McDowell, Alan Batten, Branding TV: Principles and Practices, →ISBN, page 116