badly or inadequately defined; vague: He confuses the reader with ill-defined terms and concepts.

Origin of ill-defined

First recorded in 1865–70 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for ill-defined

murky, unclear, vague, dim, indistinct, clouded, obscured

Examples from the Web for ill-defined

Contemporary Examples of ill-defined

Historical Examples of ill-defined

  • The cloud, you mean--a dim, ill-defined, dark body of vapour?

    Homeward Bound

    James Fenimore Cooper

  • There was a picture of myself sitting in an ill-defined room; that was all.

    The Worlds of If

    Stanley Grauman Weinbaum

  • The Niuans had a belief in a future state, albeit shadowy and ill-defined.

    Savage Island

    Basil C. Thomson

  • It was so ill-defined that he could not trace it to its source.


    Henry Kingsley

  • Now the duties of these Native Commissioners were multifarious, if ill-defined.

British Dictionary definitions for ill-defined



imperfectly defined; having no clear outline
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012