What is the negative adjective for suitable?

The negative adjective for "suitable" depends on the context:

If "suitable" means appropriate or fitting:

* Unsuitable

* Inappropriate

* Unfitting

* Inapplicable

If "suitable" means satisfactory or good enough:

* Unsuitable

* Inadequate

* Insufficient

* Unacceptable

If "suitable" means convenient or easy to use:

* Inconvenient

* Awkward

* Difficult

* Unwieldy

The best choice will depend on the specific meaning you want to convey.