To return to a place after having been there at a previous time.
(of two or more persons) To have known each other for a certain length of time.
Bill and I go back to college.
To extend into past time.
Bill and I have a friendship that goes back years.
(used with "on") To abandon, desert, betray or fail someone or something.
You promised me that you'd pay up today, no going back on your word.