1. Impossible to achieve
   - unachievable, unattainable, unrealizable, unrealisable [Brit]

See also: impossible

Encyclopedia: Undoable

• ascospore
• ascosporic
• ascosporous
• ascot
• ascribable
• ascribe
• ascription
• ascus
• asdic
• asea
• ASEAN
• asepsis
• aseptic
• asexual
• asexual reproduction
• asexuality
• asexually
• Asgard
• ash
• ash tree
• Ash Wednesday
• ash-blonde
• ash-gray
• ash-grey
• ash-key