competing program in the same timeslot; counterprogram
Refers to a TV or radio program scheduled opposite another station's program, often as a competitive counterprogramming strategy.
A popular drama started as a competing program in the same timeslot, so our ratings dropped.
あの局はいつも裏番組に強いバラエティをぶつけてくる。
That station always puts a strong variety show up against our program.