well-founded \ˈ ̷ ̷| ̷ ̷ ̷ ̷\adjective 1.: constructed on a solid or firm foundation < a well-founded building > 2.: having a firm foundation in fact : based on excellent reasoning, information, judgment, or grounds < hope your fears are not well-founded — Allen Upward > < a doctrine … well-founded in principle — Richard Olney >