Dictionary

A person who is incompetent.

Unskilled; lacking the degree of ability that would normally be expected.

Example: Having an incompetent lawyer may be grounds for a retrial, but the lawyer in question probably doesn't know that.

Unable to make rational decisions, insane or otherwise cognitively impaired.

Example: The charged was judged incompetent to stand trial, at least until his medication started working.

Of the cervix: opening too early in pregnancy, provoking the baby to be born.

Not resistant to deformation or flow.