indefinable in WordNet English dictionary

1. defying expression or description
   "indefinable yearnings"; "indescribable beauty"; "ineffable ecstasy"; "inexpressible anguish"; "unspeakable happiness"; "unutterable contempt"; "a thing of untellable splendor"
   indefinable  indescribable  ineffable  unspeakable  untellable  unutterable 
   
2. not capable of being precisely or readily described; not easily put into words
   "an indefinable feeling of terror"; "an abstract concept that seems indefinable"
   indefinable  undefinable