IPA: /ˌsɒlɪtjuˈdɪnəriən/
KK: /səˌlɪtʃuˈdɪnəriən/
A person who lives alone and prefers to be in solitude rather than with others.
The solitudinarian enjoyed spending his days hiking in the mountains, away from the noise of the city.
Solitudinarian is formed from "solitudo" (meaning solitude) and "-arian" (meaning one who practices or advocates). The word describes a person who prefers or advocates for solitude.
Think of someone who is an advocate for 'solitude' — that's what a solitudinarian is.