The phrase 'remains ill-defined' is a correct and usable phrase in written English.
You can use it whenever you need to describe something that remains unclear or indefinite. For example: "Despite years of research, the exact cause of the disease remains ill-defined."
The neuroimmunologic effect of traumatic head injury remains ill-defined.
As reflected by this discrepancy, the true required number for proficiency remains ill-defined.
However, ICP remains ill-defined, complicated and non-linear because it is affected by many predictable and unpredictable factors.
The burden of traumatic injuries in India is certainly high, but remains ill-defined and poorly quantified.
Despite its importance, the professional skepticism construct remains ill-defined and measurements used in research do not map well into practice.
Among these parameters, the tortuosity remains ill-defined in the field of electrochemistry, resulting in a wide range of different calculation approaches.
The Republican presidential contest remains ill defined, with no announced candidates for 2012.
That problem will become particularly acute if American commanders in Afghanistan seek even more troops for a mission that many of Mr. Obama's most ardent supporters say remains ill defined and open-ended.
Even if the concept of Catalan independence remains ill defined, Josep Ramoneda, a Catalan philosopher and writer, suggested that it was in fact "the only real political project in Spain at this moment".
Under an agreement brokered by the Obama administration, Mr. Allawi was supposed to take over a committee on national security and other strategic issues whose authority remains ill defined.
However, the subset of patients who will benefit from repeat resection in this setting remains ill defined.
