This is where you can play "Alone" by Heart, I guess. Hitoribocchi means utterly alone, or solitary. The kanji is usually seen as 一人ぼっち、but can also be written 独りぼっち、and according to my dictionary, the kanji for hitori boushi (独法師) can also be read hitoribocchi.
I was watching a news program the other day, and they were talking about the meaning of hitoribocchi. According to the news program (I suppose I should say, "According to what I believe I understood the news program to say"), the phrase comes from hitori boushi （独法師）。The first kanji there is the same kanji that you will see in "independence." Anyway, 独法師 is basically an itinerant priest or monk. The monk would travel around by himself, sent out by his monastery or what have you, or withdraw and wander around the world aimlessly and unaccompanied.
Try your hand at reading some Japanese by looking over the very brief explanation of hitoribocchi, and how the boushi of hitoriboushi became bocchi (or pocchi), by looking here.