～だす
～だす · ～dasu · JLPT N4 · noun
to start doing ~
🚪 出す = to put out: the action comes out, so it starts (降り出す = begin to rain)
出す (dasu) means to put or let out. Attached to a verb stem, the action bursts out: 泣き出す = cry + out = burst into tears, 走り出す = run + out = break into a run. English does the same with break out laughing. It often implies a sudden start.