that'll be the day

(redirected from thatll be the day!)

that'll be the day

Said of something that is unlikely to happen. Good fortune? Happening to me? Ha, that'll be the day!

That'll be the day!

Inf. It will be an unusually amazing day when that happens! Bill: I think I'll fix that lamp now. Andy: When you finally get around to fixing that lamp, that'll be the day! Sue: I'm going to get this place organized once and for all! Alice: That'll be the day!

that'll be the day

That will never happen, that's very unlikely, as in You think I'll win the lottery? That'll be the day! Presumably this phrase is short for that will be the day worth waiting for, but it is nearly always used ironically, as in the example. [Mid-1900s]

that'll be the day

COMMON People say that'll be the day to show that they think that something will never happen. `He says he's going to decorate his house.' — `Hah. That'll be the day.'

ˈthat’ll be the day

(spoken, ironic) used for saying that something is unlikely: ‘When I’m rich, I’ll buy you a new car.’ ‘That’ll be the day!’