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).
Someone weak and unimportant, a wimp.
A geek or nerd, especially a computer user with a deficient social life.
A small creature which has a low cost to put into play, often used in a swarm with other such creatures.