lacking some element or characteristic; defective

deficient in taste.

insufficient; inadequate

deficient knowledge.

a person who is deficient, esp. one who is mentally defective.

adjective

adequate , ample , enough , excessive , faultless , flawless , perfect , satisfactory , sufficient , superfluous

adjective

amiss , bad , damaged , defective , exiguous , faulty , flawed , found wanting , impaired , incomplete , inferior , infrequent , injured , insufficient , lacking , marred , meager , not cut out for , not enough , not make it , not up to scratch , outta gas , rare , scant , scanty * , scarce , second fiddle * , second string , short , shy , sketchy , skimpy , third string , unassembled , unequal , unfinished , unsatisfactory , wanting , weaknotes:defective means having a defect or fault , while deficient means inadequate or lacking in amount or degree , inadequate , under , crude , dysgenic , immature , imperfect , meagre , mediocre , minus , rudimentary , scanty , underdeveloped