1.Lit. to settle one's financial accounts with someone. I have to square accounts with the bank this week, or it'll take back my car. I called the bank and said I needed to come in and square accounts.
2.Fig. to get even with someone; to straighten out a misunderstanding with someone. I'm going to square accounts with Tom. He insulted me in public, and he owes mean apology. Tom, you and I are going to have to square accounts.