not half (something)

not half

Absolutely; I strongly agree. Primarily heard in UK, Australia. A: "Will we go down to the pub for a couple of pints?" B: "Not half!"
See also: half, not

not half (something)

A more emphatic way to say "not." Primarily heard in UK. Did you just say that 2+2=5? Geez, you're not half smart, are you?
See also: half, not
Farlex Dictionary of Idioms.

not half

1 not nearly as. 2 not at all. informal 3 to an extreme degree; very much so. British informal
See also: half, not
Farlex Partner Idioms Dictionary

ˌnot ˈhalf

(British English, informal) used to emphasize a statement or an opinion: It wasn’t half good (= it was very good). ‘Is it hot outside?’ ‘Not half. It’s much too hot for me.’
See also: half, not
Farlex Partner Idioms Dictionary

not half

Not at all: "Fancy housing? Not half likely, ma'am" (Russell Baker).
See also: half, not
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • not half
  • too (something) by half
  • too clever by half
  • too clever, quick, etc. by half
  • too something by half
  • spanked
  • hasn
  • glass
  • half the time
  • half an eye