From Longman Dictionary of Contemporary Englishnot halfnot halfBritish English spokenLOT/VERY MUCH used when you want to emphasize an opinion or statement She doesn’t half talk once she gets started. → half
Examples from the Corpus
not half• Not three, not half a dozen, not a rifle platoon.• Likewise with Relevance: if B wants three bolts, he wants them now not half an hour later.• So he was not half as earnest and solemn as she had thought him.• But I prefer to see the glass as half full, not half empty.• It's not half so mysterious when you've got a horde of parents dragging screaming kids around it.• Yet not half so tiresome as a February expedition across the fens.• The game could really have been over by about 60 mins, if not half time. 