From Longman Dictionary of Contemporary Englishill-foundedˌill-ˈfounded adjective formal UNTRUEbased on something that is untrue His fears proved ill-founded.
Examples from the Corpus
ill-founded• But any doubts about Marillion's future were clearly ill-founded.• The experience of the 1970s, further, demonstrated that the principal argument in favour of flexible exchange rates was ill-founded.• Suppositions built on postcards and photographs might be as ill-founded as his short-lived suspicions of being followed the night before.• The trouble is that the revised version of the legend of the Courts of Love is as ill-founded as the old one.• The whole enterprise was ill-founded from the start.• But the case of Auerbach merely serves to illustrate how ill-founded the criterion is.• ill-founded worries 