When something breaks out, it begins suddenly and often spreads quickly. A fire might break out in a building, forcing everyone to evacuate. A fight could break out on the playground when an argument gets out of control. During history class, you might learn how World War I broke out in 1914 after years of tension between European nations.

The phrase suggests something happening unexpectedly or explosively, like when laughter breaks out during a solemn assembly because someone made a funny noise. Disease can break out in a community, riots can break out in a city, or even acne can break out on someone's face during their teenage years.

Break out can also mean escaping from confinement. Prisoners might break out of jail (though they usually get caught!). After being stuck indoors during a rainstorm all weekend, you might feel ready to break out and finally play outside.

There's also the expression breakout success, which describes someone or something that suddenly becomes very popular or successful, like an unknown actor having a breakout role in a movie that makes them famous, or a band having a breakout hit that everyone suddenly knows.