A splitter is something that divides one thing into separate parts. A log splitter is a tool that cuts firewood into smaller pieces. Cable splitters divide a television or internet signal so it can go to multiple rooms in a house. In baseball, a splitter is a type of pitch that suddenly drops as it reaches home plate, seeming to split the distance between the pitcher's mound and the batter.

You might split a candy bar with a friend, split wood for a campfire, or watch a magician seemingly split a person in half. Sometimes groups split up when they disagree about something important, like when a club divides into two separate organizations.

There's also an interesting use in philosophy and science: a hair-splitter is someone who argues about tiny, unimportant differences. If you and a friend debate whether something is “blue” or “navy blue” for ten minutes, you're splitting hairs. The phrase suggests making distinctions so fine they don't really matter, like trying to cut a single hair lengthwise.