hysterical laughter 

To come face to face with an epiphany moment that results in an instantaneous burst of uncontrollable laughter for a prolonged period of time.

I suppressed the thought of being pregnant while getting through final exams followed by a trip to the pharmacy. As soon as I saw the result of my pregnancy test I broke out into hysterical laughter.

hysterical laughter by MAM803 May 3, 2016