hidden, unknown, invisible, indiscernible, unnoticeable, anonymous, nonmaterial, secret, insensible, intangible asset, knowledge, obscure, strange, mysterious, ephemeral, imperceptible, nonphysical, indistinguishable, private, unidentifiable, personal, unobservable, intangible assets, airy, inappreciable
immaterial (part of speech: adjective)
unsubstantial (part of speech: adjective)
uncertain (part of speech: adjective)
- Rather an intangible fortune, isn't it?
- Nothing of an exciting nature had happened in several months, and, but for his intangible misgivings, there was no sign of an interruption to his tranquil life. - "The Gray Phantom's Return", Herman Landon.
- It was as if a violet had been born to actual bloom from the thought, the intangible vision of one. - "The Other Girls", Mrs. A. D. T. Whitney.