One-way mirror, a glass through which one can see only in one way
One way in travel means purchashing a ticket for a single direction of travel. No ticket is purchased for a return to the starting location for the trip.
One Way as a proper noun may refer to:
One Way (album), Australian R&B singer Selwyn's second album
One Way (band), R&B/funk band popular from late 1970s through the 1980s