From Longman Dictionary of Contemporary Englishnot a jotnot a jotold-fashionedNOT not at all or none at all There was not a jot of humour in the man. → jot
Examples from the Corpus
not a jot• But Lewis devises a strategy, pursues it, and cares not a jot if the crowd does not approve.• It was at once apparent to Joan that, whatever changes of circumstance had taken place, he had changed not a jot.• Do not jot down figures which have little basis in fact.• Older he undoubtedly is, but he is not a jot wiser.• Six out of 10 voters are still not buying and three weeks of slogging seem to have made not a jot of difference.• Legally this matters not a jot.• There was not a jot of humour in the man. 