Webster's 1828 Dictionary
UNIMAGINABLE
a.Not to be imagined; not to be conceived.
New American Oxford Dictionary
unimaginable
un im ag i na ble |ˌənəˈmaj (ə )nəbəl ˌənəˈmæʤ (ə )nəbəl | ▶adjective difficult or impossible to imagine or comprehend: lives of almost unimaginable deprivation. DERIVATIVES un im ag i na bly |-blē |adverb
Oxford Dictionary
unimaginable
un |imagin ¦able |ʌnɪˈmadʒɪnəb (ə )l | ▶adjective difficult or impossible to imagine or comprehend: lives of almost unimaginable deprivation. DERIVATIVES unimaginably adverb
American Oxford Thesaurus
unimaginable
unimaginable adjective the phone bills have been unimaginable: unthinkable, inconceivable, indescribable, incredible, unbelievable, unheard of, unthought of, untold, mind-boggling, undreamed of, beyond one's wildest dreams.
Oxford Thesaurus
unimaginable
unimaginable adjective unimaginable riches: unthinkable, inconceivable, incredible, unbelievable, unheard of, unthought of, unspeakable, unutterable, untold, ineffable, implausible, improbable, unlikely, impossible, undreamed of, beyond one's wildest dreams, beyond the realm of reason; astounding, amazing, astonishing, fantastic, fabulous, breathtaking, overwhelming, staggering; informal mind-boggling, mind-blowing.
Sanseido Wisdom Dictionary
unimaginable
ù n im á g i na ble 形容詞 想像できない, 思いもよらない .