one-way

adjective

• moving or allowing movement in one direction only:a one-way valve
• (of a road or system of roads) along which traffic may pass in one direction only.
• (of a ticket) allowing a person to travel to a place but not back again.
• (of glass or a mirror) seen as a mirror from one side but transparent from the other.
• denoting a relationship in which all the action or contribution of a particular kind comes from only one member:interaction between the organism and the environment is not a one-way process