indefinable /in-di-fīˈnə-bl/

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

• cuneiform
• cuneiform bones
• cuneiforms
• cunette
• cunettes
• cunjevoi
• cunjevois
• cunner
• cunners
• cunnilinctus
• cunnilinctuses
• cunnilingus
• cunnilinguses
• cunning
• cunninger
• cunningest
• cunningly
• cunningness
• cunningnesses
• cunnings
• cunt
• cunts
• cup
• CUP
• cup-and-ball