What is an other word for impossible?

Here are some other words for "impossible," depending on the context and nuance you want to convey:

Formal:

* Impractical

* Unfeasible

* Infeasible

* Unattainable

* Utopian

* Inconceivable

* Improbable (less extreme than impossible)

Informal:

* Out of the question

* No way

* Not a chance

* Unthinkable

* Beyond the realm of possibility

Figurative:

* A pipe dream

* A long shot

* A wild goose chase

The best word to use depends on the specific situation and the level of formality you require.