unknown

nouns

an unknown and unexplored region
"they came like angels out the unknown"
anyone who does not belong in the environment in which they are found
a variable whose values are solutions of an equation

adjectives

not known
"an unknown amount"; "an unknown island"; "an unknown writer"; "an unknown source"
antonym
is similar to
(of unknown regions) not yet surveyed or investigated
"uncharted seas"
is similar to
unknown to most people
is similar to
(usually used with `to') occurring or existing without the knowledge of
"a crisis unbeknown to me"; "she had been ill for months, unbeknownst to the family"
is similar to
eluding diagnosis
"undiagnosed disease"
is similar to
not yet discovered
"undiscovered islands"
is similar to
previously unknown
"a first novel by an unheard of writer"; "developments on an unheard-of scale"
is similar to
not yet identified
"an unidentified species"; "an unidentified witness"
see also
not recognized or admitted
see also
not known or well known
"a name unfamiliar to most"; "be alert at night especially in unfamiliar surroundings"
see also
not bringing honor and glory
"some mute inglorious Milton here may rest"
being or having an unknown or unnamed source
"a poem by an unknown author"; "corporations responsible to nameless owners"; "an unnamed donor"
not known to exist
"things obscurely felt surged up from unknown depths"
is similar to
not suspected or believed likely
"remained unsuspected as the head of the spy ring"; "he was able to get into the building unspotted and unsuspected"; "unsuspected difficulties arose"; "unsuspected turnings in the road"
not famous or acclaimed
"an obscure family"; "unsung heroes of the war"
not known before
"used many strange words"; "saw many strange faces in the crowd"; "don't let anyone unknown into the house"