little, slight, small
high-pitched
hysterical, nervous
girlish

give, let out
stifle, suppress
I just managed to stifle a giggle at the absurd idea.

hear

with a giggle
‘Age before beauty!’ she said with a giggle.

giggle about, giggle at
We shared a giggle about the new office romance.

collapse into giggles, dissolve into giggles
We all collapsed into giggles.

a fit of (the) giggles
get the giggles (esp. BrE), have the giggles (esp. AmE)
Alison tends to get the giggles at the most inappropriate moments.
She still has the giggles about the experience.

have a giggle (esp. BrE), share a giggle (esp. AmE)
They all had a giggle at my expense.
We shared a giggle at their predicament.

helplessly, hysterically, nervously, uncontrollably
The children giggled hysterically.

about
They giggled about their teacher's accident.

at
We giggled at the picture.

over
We were giggling over some old photos.

with
The children giggled with delight.

a fit of giggling
They collapsed in a fit of giggling.