What is hair trigger?

I was shooting my semi auto last night and I squeezed the trigger once and then let the trigger reset again and squeezed it again and let off 2 shots of semi auto. but my question is is there a faster way to empty my clip besides every time I squeeze the trigger a round comes out? how do you use the hair trigger?... show more I was shooting my semi auto last night and I squeezed the trigger once and then let the trigger reset again and squeezed it again and let off 2 shots of semi auto. but my question is is there a faster way to empty my clip besides every time I squeeze the trigger a round comes out? how do you use the hair trigger? like do you squeeze once and dont let the trigger come back and just keep squeezing?
Update: Ok. Thank you all for your answers. My gun has a hair trigger than. I was just mixed up I thought some semi autos had a different feature. WellI learned something. Thanks.
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