To do the unthinkable means to do something unexpected.
Impossible to imagine; inconceivable.
Unreasonable; improbable; not to be considered; out of the question.
1. This store is doing the unthinkable and making their products more affordable.
2. Skateboarding isn’t what it used to be, a lot of boarders are doing the unthinkable.
3. Olympic athletes are in a different league, breaking records and doing the unthinkable.
4. It’s possible that big corporations are doing the unthinkable and stealing our money legally now.
absurd, beyond belief, beyond possibility, exceptional, extraordinary, illogical, implausible, impossible, improbable, inconceivable, out of the question, outlandish, preposterous, rare, unbelievable, uncommon, unimaginable, unlikely, unreasonable