Idiom
burst in on someone or something
Theme: INTERRUPTION
to enter a room, interrupting someone or some activity. (Often without knocking or seeking permission to enter.)Tom burst in on his sister and her boyfriend while they were kissing.I must ask you not to burst in on a board meeting again. Whatever it is can wait.
Idiom
burst in onburst in (on someone/something)
to enter or appear suddenly or unexpectedly.She was in the middle of teaching her writing class when the head of the English department burst in.“Sorry to burst in on you like this,” Nick apologized to the room full of surprised people.