Definition of all one:
(adj) :
by one's self; apart from, or exclusive of, others; single; solo; solitary;—applied to a person or thing; of or by itself; by themselves; without any thing more or any one else; without a sharer; only
"I can't ask for help because I am alone. That is, “I am alone” means nobody else is near."
(v) :
by one's self; apart from, or exclusive of, others; solo
"she walked home alone."