What is the definition of tacitum?

"Tacitum" is not a recognized English word. It's possible there's a typo or you are thinking of a different word.

Here are some possibilities based on the spelling and possible meanings:

* Tacit: This is a word that means understood or implied without being stated. For example, "There was a tacit agreement between the two parties."

* Tacitum could be a Latin word, possibly a misspelling of "tacitum," which is the neuter singular accusative form of the adjective "tacitus," meaning silent or unsaid.

If you can provide more context or the original source where you saw "tacitum," I might be able to give you a more precise answer.