pluck something out of the air

pluck (something) out of the/thin air

To say or produce something haphazardly or at random, rather than through careful consideration or calculation. Look, this legislation hasn't been plucked out of thin air. We've spent months crafting the bill to best serve all of our citizens. Her ability to ad lib is so remarkable that it's hard to believe she's plucking these jokes out of the air.
See also: air, of, out, pluck, thin
Farlex Dictionary of Idioms.

pluck something out of the ˈair

say a name, number, etc. without thinking about it, especially in answer to a question: I just plucked a figure out of the air and said: ‘Would £1 000 seem reasonable to you?’
See also: air, of, out, pluck, something
Farlex Partner Idioms Dictionary
See also:
  • pluck (something) from the air
  • pluck (something) out of the/thin air
  • pluck something from the air
  • pull (something) out of the/thin air
  • pluck up
  • slap onto
  • chuck (something) in (to something)
  • chuck in
  • all over the lot
  • draw straws for (something)