1
general::
1. Make a forcible entry into, as in The alarm went off as soon as they tried to break into the house. [1300s] Also see BREAK IN, def. 1. 2. Interrupt, as in I couldn't help but break into your conversation. [Mid-1600s] 3. Suddenly begin some activity, as in Without warning she broke into tears. Also see under BURST INTO. 4. Enter or be admitted to an occupation or profession, as in Without connections it is virtually impossible to break into acting. [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): break into something
to begin to perform or utter suddenly, especially with song, speech, chattering, tears, etc. • Suddenly, she broke into song. • As soon as the movie started, the people behind me broke into loud chattering.
McGrawhill's American Idioms And Phrasal Verbs