Ghareeb is an Arabic word which means a stranger. Ghreebul Ghuraba means the the stranger of the strangers.
We have authentic narrations in Kaamil Al-Ziyarat by Ibn Qowlawayh mentioning great reward for visiting Imam Ali Riza (AS) in his far away place في غربته. Which means that he is Ghareeb in the place where he is.
Wassalam.