to secretly think that something is funny
to laugh up one's sleeve
to not smile or laugh
to keep a straight face
looking very happy, especially soon after you have been looking worried or sad
to be all smiles
to play a joke on somebody, usually by making them believe something that is not true
to pull somebody's leg
to say funny things with a serious, calm expression
to have a dry sense of humour
to find something extremely funny
to roll on the floor laughing/to die laughing
a person that everyone laughs at because they have done something stupid
a laughing stock