unexplained (adj.)
- able
- enigmatic
- incalculable
- incognizable
- invisible
- mysterious
- puzzling
- sealed
- strange
- unapparent
- unbeknown
- uncharted
- unclassified
- undetected
- undisclosed
- undiscoverable
- undiscovered
- unexplored
- unfamiliar
- unfathomed
- unheard
- unheard-of
- unidentified
- unknowable
- unknown
- unperceived
- unplumbed
- unrevealed
- unseen
- unsolved
- unsuspected
- untouched
- untracked
- virgin
