- unrevealed
- undisclosed
- untold
- undivulged
- secret
- unspecified
- dark
- mysterious
- concealed
- hidden
- undecided
- undetermined
- unfixed
- unresolved
- unsettled
- unestablished
- pending
- unsure
- undefined
- unascertained
- inconclusive
- indefinite
- in limbo
- in the balance
- unexplored
- up in the air
- unmapped
- uncharted
- undiscovered
- untravelled
- remote
- virgin
- outlandish
- exotic
- unnamed
- unidentified
- anonymous
- nameless
- incognito
- undesignated
- unfamiliar
- innominate
- unprecedented
- unheard of
- novel
- new
- obscure
- strange
- unsung
- little known
- insignificant
- minor
- undistinguished
- unimportant
- inconsequential
- unrenowned
- unhonoured
- lowly
- forgotten
Example Sentences of Unknown
1. The sender's identity remains unknown still.
2. They ventured into unknown territory bravely.
3. The cause of illness is unknown.
4. An unknown error occurred during processing.