Other forms: manos a manos
Something that's mano a mano happens directly, or face to face. If you want to settle an argument with your friend mano a mano, you hope for an in-person conversation with her.
Mano a mano means "hand to hand" in Spanish, and it originally referred to a physical fight at close range. While it can still describe an up-close altercation, you can also use it for any kind of face-to-face confrontation, like candidates clashing mano a mano on a debate stage. Don't make the common mistake of confusing mano a mano with "man to man," which describes an honest conversation between two people.