[laugh] like a drain

to laugh really loudly and in length

The origin of the idiom "laugh like a drain" is unclear, but it is believed to have evolved as a humorous and whimsical expression to describe someone who is laughing heartily and loudly. The phrase combines the idea of laughter, which is often associated with joy and amusement, with the sound of water draining, which can be loud and continuous. It is used to emphasize the intensity of someone's laughter and the infectious nature of their amusement.

When Sarah told her hilarious joke, the whole room laughed like drains, and the laughter was infectious.
The comedy show was so funny that the audience laughed like drains throughout the performance.
After a long and stressful week, John and his friends met up to share funny stories and laugh like drains at the local pub.
The unexpected antics of the circus clown had the children laughing like drains, filling the tent with joyous sounds.
During the school assembly, the principal shared a light-hearted story that had the students and teachers laughing like drains.