A person who is incompetent.
Not resistant to deformation or flow.
Unable to make rational decisions; insane or otherwise cognitively impaired.
Opening too early during pregnancy, resulting in miscarriage or premature birth.
Unskilled; lacking the degree of ability that would normally be expected.
Somebody who is inept, or lacking in skill, or talent.
Not adroit; awkward, clumsy, inept.