Question: I don't know if it's heartless,but when I'm in a situation that is really sad(like a funeral) I always have this urge to laugh.Of course I try not to burst out in laughter but I guess it's how I cope with these things.

Is there a word that can describe this?I don't mind if it would be used for the urge,the behaviour,the feeling.I'm just really interested how to express this kind of thing without having to say that I really,really have to laugh.

Answer: 
I'd describe that as a fit of [hysterical](http://dictionary.reference.com/browse/hysterical) laughter :

Hysterical:

> 
> * uncontrollably emotional.
> * irrational from fear, emotion, or an emotional shock.
> 
> 
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( from dictionary.reference.com)
Titter

to laugh nervously, often at something that you feel you should not be laughing at.