burst in
(on someone or something) 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 askyou not to burst into my office again. Whatever it is can wait.
burst in
((up)on someone or something) Fig. to intrude or come in thoughtlessly and suddenly and interrupt someone or something. (Upon is formal and less commonly used than on.) I didn't mean to burst in on you. She feared that someone would burst in upon her.
burst in
(with something) to interrupt with some comment. Ted burst in with the good news. He burst in to tell us about his new car.
burst in (to some place)
Fig. to intrude or come in thoughtlessly and suddenly. Ted burst into the room and sat down right in the middle of the meeting. Wasn't it very annoying of him to just burst in?