A person who is deficient.
Insufficient or inadequate in amount.
Lacking something essential; often construed with in.
Of a number n, Having the sum of divisors σ(n)<2n, or, equivalently, the sum of proper divisors (or aliquot sum) s(n).
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.