Undefined
Part of speech: adjective
Definition: Lacking a definition or value That does not have a meaning and is thus not assigned an interpretation (for example, division by zero)
Example sentence: The sea has this contradictory quality, that the more you see of it, the more it overwhelms the eye and disappears in its own brightness. Like a flame, whose meaning is light but whose centre is dark, it demands to be undefined.
Undefinable
Part of speech: adjective
Definition: Not definable