Emily Dickinson Lexicon

back (-s), n. [OE.] (webplay: “come back”, face, fall, forget, natural, thickest, “turn the back”).

1. Unseen upper part; [fig.] boundary; far side; outer form.
2. Upper posterior side; shoulder and spinal cord area; dorsal part of the human body.
3. Phrase. “Turn one's back”: reject; withdraw from.