Steal somebody’s thunder
Definition 1 of 1
Pro Tip 1/3Attention Grabbing
Used when someone unintentionally or intentionally takes the spotlight from another person. 
Just as Julia was about to give her speech, Mark stole her thunder by revealing the surprise guest.
Pro Tip 2/3Negative Connotation
Often implies doing something rude or inconsiderate, even if not intended. 
During the team meeting, Tom stole Linda's thunder by interrupting her with his own suggestions.
Pro Tip 3/3Enhanced Impact
The action that steals thunder tends to be more dramatic or unexpected than the overshadowed event. 
Her stunning performance at the close of the ceremony completely stole her colleague's thunder.