arcane
cabalistic
extraordinary
impenetrable
improbable
inscrutable
more than expected
mystic
numinous
out-of-the-way
past expectation
sudden
unaccountable
unannounced
unanticipated
undivined
unexpected
unforeseeable
unforeseen
unheralded
unhoped for
unknowable
unpredictable
unpredicted
unprepared for
without warning
holpen
unassailed
unattained
uncollected
undescribed
undisclosed
undiscovered
undreamed-of
unexperienced
unexplored
unexposed
unfelt
unguessable
unimagined
unimpeached
unread
unreckoned
unrecorded
unreleased
unrevealed
unsuspected
unthought-of
unutilized