un ‧ dreamed-of /ʌnˈdriːmd- ɒv $ -ɑːv/ BrE AmE ( 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.
un ‧ dreamed-of /ʌnˈdriːmd- ɒv $ -ɑːv/ BrE AmE ( 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.
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012