* It's a misspelling: It could be a misspelling of a real word, like "tablets," "tabards," "tambours," or something else entirely.
* It's a slang term: It might be a slang word specific to a particular group or region.
* It's a made-up word: The person you heard it from might have invented it for a specific purpose or as a joke.
To figure out the meaning, you need more context. Can you provide more information about where you heard this word?
For example:
* Who said it?
* What were they talking about?
* What was the situation?
With more context, I might be able to help you figure out what "tabnabs" means.