Solivagant. \sōˈlivəgənt\

Both a noun and adjective.

To begin with the Latin, where everything begins…

The prefix:

soli-, sol-

(Latin: one, alone, only)

And the suffix:

vaga-, vag-, vago-

(Latin: wander, move around; unsettled, wandering [nerve])

Thank you, Professor Kobleske. My years of Latin still pay off.