1. Incapable of being ascended
   - unscalable 
2. Incapable of being surmounted or climbed
   - unsurmountable

See also: impassable, unpassable

• Antrozous
• Antrozous pallidus
• antrum
• antsy
• Antum
• Antwerp
• Antwerpen
• Anu
• Anubis
• Anunnaki
• Anura
• anuran
• anuresis
• anuretic
• anuria
• anuric
• anurous
• anus
• Anvers
• bifocals
• bifoliate
• biform
• bifurcate
• bifurcated
• bifurcation