What word means descriptive of something that has not come before?

There are several words that could describe something that has not come before, depending on the specific nuance you want to convey. Here are a few options:

General:

* Novel: This is a common word that simply means new and original.

* Unprecedented: This word implies that something has never happened before.

* Unparalleled: This word emphasizes that something is unique and unmatched.

More specific:

* Pioneering: This word suggests that something is groundbreaking and innovative.

* Revolutionary: This word implies that something is a radical departure from the old ways of doing things.

* Avant-garde: This word refers to something that is at the forefront of new developments, often in art or culture.

* Uncharted: This word suggests that something is unexplored and unknown.

The best word to use will depend on the context of your sentence.