From Longman Dictionary of Contemporary Englishill-definedˌill-deˈfined adjective 1 CLEAR/EASY TO UNDERSTANDnot described clearly enough Some jobs in the company are pretty ill-defined.2 CLEAR/EASY TO SEEnot clearly marked, or not having a clear shape SYN indistinct The borders were vague and ill-defined.
Examples from the Corpus
ill-defined• The procedures are ill-defined and completely untested.• With other semi-regular stars, the periods are so ill-defined as to be barely recognizable, and sometimes the fluctuations become random.• an ill-defined border• I will seek to show that it is confined within narrow, if ill-defined, bounds.• She shivered at some ill-defined idea, drifting past out of reach, in the foggy recesses of her mind.• Government documents and official statements concerning integration are replete with romantic and ill-defined language.• Above the scoop neckline of her peacock blue dress, an ill-defined rash of mottled pink broke out, then faded.• The few planetaries bright enough to be seen with binoculars show up in the guise of dim, ill-defined stars.• They constitute an assortment of ill-defined symptoms that affect people in different ways and to different extents. 