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

See also: impossible

• regality
• regally
• regard
• regard as
• regardant
• regarder
• regardful
• regarding
• regardless
• regards
• regather
• regatta
• regency
• regeneracy
• regenerate
• regenerating
• regeneration
• regenerative
• regenerator
• regent
• regex
• reggae
• Reggane
• regicidal
• regicide