The Collaborative International Dictionary of English v.0.48:

Insufficient \In`suf*fi"cient\, a. [L. insufficiens, -entis. See
   In- not, and Sufficient.]
   [1913 Webster]
   1. Not sufficient; not enough; inadequate to any need, use,
      or purpose; as, the provisions are insufficient in
      quantity, and defective in quality. "Insufficient for His
      praise." --Cowper.
      [1913 Webster]

   2. Wanting in strength, power, ability, capacity, or skill;
      incompetent; incapable; unfit; as, a person insufficient
      to discharge the duties of an office.

   Syn: Inadequate; scanty; incommensurate; unequal; unfit;
        incompetent; incapable; inefficient.
        [1913 Webster]

WordNet (r) 3.0 (2006):

insufficient
    adj 1: of a quantity not able to fulfill a need or requirement;
           "insufficient funds" [syn: insufficient, deficient]
           [ant: sufficient]