indefinable /in-di-fīˈnə-bl/

1. That cannot be defined
2. Hard to identify or describe

• kneehole
• kneeholes
• knee-holly
• kneeing
• knee-jerk
• knee-jerks
• knee joint
• knee joints
• kneel
• kneeled
• knee-length
• kneeler
• kneelers
• kneeling
• kneels
• knee-pad
• knee-pads
• knee-pan
• knee-pans
• knees
• knee sock
• knee socks
• knee-stop
• knee-stops
• knees-up