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

See also: impassable, unpassable

• enchantment
• enchantress
• encharge
• enchase
• enchilada
• enchiridion
• enchondroma
• encipher
• encircle
• encircled
• encirclement
• encircling
• enclave
• enclitic
• enclose
• enclosed
• enclosed space
• enclosing
• enclosure
• enclothe
• encode
• encoder
• encoding
• encolure
• encomiast