From Longman Dictionary of Contemporary Englishnot that ...not that ...used before a sentence or phrase to mean the opposite of what follows it, and to make the previous sentence seem less important Sarah has a new boyfriend – not that I care (=I do not care). Janice had lost some weight, not that it mattered (=it did not matter). → not
Examples from the Corpus
not that ...• We thought Charlie was not that close to the camp.• Stanford was a 28-22 loser at Arizona Stadium, and it was not that close.• Bringing past legends to life is not that easy but Simon Cadell is astonishingly successful as Coward.• Himself, and not Paul, and certainly not that kid out there.• It was the wealth of the new entrepreneurs, not that of their workmen, which was everywhere celebrated.• It is not that such a fuel can not be produced, so much as the scale of production required.• Moustaches were allowed, not that they did much for a few who grew them. 