A kind of laugh that is quiet and not very loud.
When someone nickers, they might be laughing at something funny but not making a big noise about it.
Examples:
She nickers at the joke.
The little girl nickers when she sees the puppy.
He nickers when he hears the silly song.
The horse nickers when it sees the carrot.
The baby nickers at the funny face.
The cat nickers at the bird outside.