Impracticable means impossible or extremely difficult to actually do or carry out. When something is impracticable, it might sound good in theory but can't work in real life because of practical obstacles that can't be overcome.

Suppose your class wants to visit the International Space Station for a field trip. That plan is impracticable: even if your teacher loved the idea, there's no realistic way to arrange it. Or imagine a recipe that requires ingredients from five different countries, all of which must be used within an hour of being picked. Following that recipe would be impracticable for almost anyone.

The word is often confused with impractical, but there's a useful distinction. Something impractical is possible but unwise or inconvenient (like wearing a ball gown to gym class), while something impracticable simply cannot be done (like building a ladder to the moon). When engineers say a design is impracticable, they mean it violates the laws of physics or requires resources that don't exist, rather than being merely a poor choice.

When you're brainstorming solutions to a problem, recognizing which ideas are impracticable helps you focus your energy on plans that might actually succeed.