The Collaborative International Dictionary of English v.0.48:
Undreamed \Un*dreamed"\, Undreamt \Un*dreamt"\, a. Not dreamed, or dreamed of; not th?ught of; not imagined; -- often followed by of. [1913 Webster] Unpathed waters, undreamed shores. --Shak. [1913 Webster]WordNet (r) 3.0 (2006):
undreamt adj 1: not imagined even in a dream [syn: undreamed, undreamed of, undreamt, undreamt of, unimagined]