It's possible that:
* It's a misspelling: It might be a typo or a mishearing of a real musical term, like "mezza forte" (medium loud) or "tutti" (all instruments play together).
* It's a specific instruction: It could be a unique term used by a specific composer or musical group.
* It's a slang term: It's possible it's an informal term within a specific musical community.
To understand its meaning, you would need more context.
Could you provide more information about where you encountered this term?
* What piece of music were you looking at?
* Who used the term?
* What was the context?
With more information, we might be able to decipher the meaning of "megatron tutti."