Basically it's a way to say lol, without having to say lol. It's great.
*plays on* - "RING DING DING DING DING BAW BAW RING BEE BEE BO POW POW WHA WHA"
Person 1: ha...
Definition 2 : An expression that meant something said wasn't funny, or just gave you a little chuckle. Maybe even just said to make yourself look not mean.
Def 2 :
Person 1 : It was like sooo funny!!
Person 2 : Ha....