- indefinable, undefinable - not capable of being precisely or readily described; not easily put into words; "an indefinable feeling of terror"; "an abstract concept that seems indefinable"
Antonym: defined (indirect, via undefined)
- indefinable, indescribable, ineffable, unspeakable, untellable, unutterable - defying expression or description; "indefinable yearnings"; "indescribable beauty"; "ineffable ecstasy"; "inexpressible anguish"; "unspeakable happiness"; "unutterable contempt"; "a thing of untellable splendor"
Antonym: expressible (indirect, via inexpressible)