adjective [ usually before noun ]
1.
moving or allowing movement in only one direction :
one-way traffic
a one-way street
a one-way valve
2.
( especially NAmE ) = single (5)
3.
operating in only one direction :
Theirs was a one-way relationship (= one person made all the effort) .
They observed the prisoners through a one-way mirror (= a mirror that allows a person standing behind it to see through it) .