when pigs fly
if pigs had wings
at no time
at latter Lammas
when two Sundays come together
when two Sundays meet
not while pussy's a cat
never ever
nevah
nary
never've
in a pig's eye
nooit
under no circumstances
nevermore
in no way
Neveruary
nauther
nother
once in a purple moon
when Hell freezes over
inexistent
unreddened
uneverted
second Tuesday of the week
unvenial
undying
unrelenting
deathless
immortality
relentless
persistent
unvisited
only if
only
only when
under no circumstance
seldom or ever
not on your life
no chance
no way
in a pig's arse
divent
not for the world
nonlitigable
not by a blame sight
non-con
not by a long sight
by no means
not a chance