a soft giggle
A soft giggle is when you laugh like you’re trying not to be noticed. It’s like a laugh that’s hiding from the world.
He did a soft giggle when I told him I saw a ghost. He didn’t want to laugh out loud.
She did a soft giggle when I told her my dog could sing. She didn’t want to believe me.
I did a soft giggle when I saw my dog wearing a suit. It was too funny to ignore.