undreamed-ofun‧dreamed-of /ʌnˈdriːmd- ɒv $ -ɑːv/ (also un‧dreamt-of /ʌnˈdremt-/) adjective 
much more or much better than you thought was possible: 
undreamt-of success Men were becoming interested in fashion on a scale undreamed-of in the 1960s.
much more or much better than you thought was possible: undreamt-of success Men were becoming interested in fashion on a scale undreamed-of in the 1960s.