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 of weak character, lacking in courage and/or moral strength.
A person of weak or even sickly physical constitution
weak, either physically, morally or mentally