The term "three-way" has multiple meanings depending on its context.
1) In a general sense, it can refer to any situation or agreement involving three parties or elements. For example, a "three-way tie" in sports refers to when two teams are tied for first place and another team is also tied with one of the top two teams.
2) In a more specific sense, "three-way" can refer to a type of sexual activity where three people engage in simultaneous oral, anal, or vaginal penetration. This practice is often referred to as "threesome."