Synonyms of undreamed of in English:

undreamed of

(also undreamt of)

See definition of undreamed

adjective

1‘he raised the party's profile to undreamed-of heights’

SYNONYMS
unexpected, unforeseen, unanticipated, not bargained for, unhoped-for, unsought, unlooked-for, unpredicted
unintentional, unintended, inadvertent, unplanned, unpremeditated, unwitting, fortuitous, chance, coincidental, serendipitous, random, fluky
sudden, abrupt, surprise, surprising, without warning, without notice, startling, astonishing, out of the blue
ANTONYMS

deliberate, planned