* It's a misspelling: Perhaps you meant a word like "plumber," "plunger," or "plumpter."
* It's a regional dialect word: Some words have local usage and are not widely known.
* It's a made-up word: Maybe it's a joke or a term specific to a particular group or context.
To help me understand what you mean, could you please provide more context?
For example:
* Where did you encounter the word "plunter"?
* What was the sentence it was used in?
* What did you think it meant?
With more information, I can help you figure out the intended meaning.