indefinable /in-di-fīˈnə-bl/

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

• characteristic curve
• characteristic curves
• characteristic function
• characteristic radiation
• characteristics
• characteristic spectrum
• characteristic X-rays
• characterization
• characterize
• characterized
• characterizes
• characterizing
• characterless
• characterlessness
• characterologist
• characterologists
• characterology
• character part
• character parts
• character recognition
• characters
• character sketch
• character sketches
• character witness
• character witnesses