What it means
A troublemaker is the one who can't resist stirring things up, the kid at the back winding everyone up, the colleague who drops the awkward question just to watch the room squirm. Sometimes it's malicious, often it's just mischief, but wherever they go a little chaos tends to follow. Half the time they're grinning while everyone else groans.
Usage examples
"Sit him away from his mates, he's a right troublemaker when they're together."
"She got a reputation as a troublemaker just for asking the questions nobody else dared."
"Don't invite Jay if you want a quiet night, that man's a troublemaker on purpose."
"He was always the class troublemaker, chatting rubbish and getting everyone else dragged into it."
Where it comes from
This one’s old and plainspoken. It’s built from trouble plus maker, literally a person who makes trouble. English has used it since the 1500s for someone who causes disruption, stirs people up, or keeps hassle in circulation, whether they’re properly malicious or just a chaos-loving little goblin.