steal someone's thunder

verb2

•
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
•
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

forms

stole someone's thunder · stolen one's thunder · stolen someone's thunder · stealing someone's thunder · steals one's thunder · steals someone's thunder