solitary
noun
confinement of a prisoner in isolation from other prisoners
“he was held in solitary”
Synonymssolitary confinementone who lives in solitude
adjective
characterized by or preferring solitude
“a lone wolf”
“a lonely existence”
of plants and animals; not growing or living in groups or colonies
“solitary bees”
lacking companions or companionship
“he was alone when we met him”
“she is alone much of the time”
being the only one; single and isolated from others
“the lone doctor in the entire county”
“a lonesome pine”
devoid of creatures
“a lonely crossroads”
“a solitary retreat”
Source: WordNet 3.1, Princeton University
