From Longman Dictionary of Contemporary Englishnot ... just/quite the oppositenot ... just/quite the oppositeOPPOSITE/REVERSEused to say that something is completely different from what has just been said I didn’t feel sleepy at all – just the opposite, in fact. → opposite
Examples from the Corpus
not ... just/quite the opposite• His falsity and hollowness are not just the opposite of the true and the wholesome, but threaten to undermine it. 