The term "Boo!" is an onomatopoeic expression that means to startle or scare someone by making a sudden loud noise, often accompanied with a clap. It can also be used as a verb to mean frightening or surprising someone.
Usage examples
At a Halloween party, someone jumps out from behind a corner and exclaims "Boo!"
During a horror movie, one character whispers "Boo" to scare their friend sitting next to them in the dark.
Lee tried to prank their sibling by hiding under the bed and shouting "Boo!" when they passed by.
At a sports game, fans might cheer for their team by shouting "Boo" at the opposing team.
When someone tells a funny joke, another person might respond with a playful "Boo!" to show their excitement.
During a magic show, the magician might say "Boo" as part of their act to surprise the audience.
A child might dress up as a ghost for Halloween and go trick-or-treating saying "Boo" instead of "Trick or treat."
When reading a scary story to a group, the storyteller might pause and say "Boo" to create suspense and frighten the listeners.
At a comedy show, the comedian might interact with the audience and playfully say "Boo" in response to a humorous comment.
This has spilled over into some angry but small in - match protests directed at Arsene Wenger and occasional bouts of booing of the team. (justarsenal.com)
This isn't a case of «we'll get use to it because we have to» its «go - away heat», a term used when professional wrestlers aren't getting booed by fans because they're good at being a bad guy but because the fans genuinely feel like their time is being wasted. (gimmegimmegames.com)
Maria Elena Salinas The Univision anchor said journalists were often unfairly vilified by politicians, mentioning Trump, and was met with boos from the audienceat California State University, Fullerton on May 22. (fortune.com)