also back door
1.
You can use ~ to describe an action or process if you disapprove of it because you think it has been done in a secret, indirect, or dishonest way.
He did the ~ deals that allowed the government to get its budget through Parliament on time...
He brushed aside talk of greedy MPs voting themselves a ~ pay rise.
= underhand
ADJ: ADJ n disapproval
2.
If you say that someone is doing something through or by the ~, you disapprove of them because they are doing it in a secret, indirect, or dishonest way.
Dentists claim the Government is privatising dentistry through the back door.
N-SING: the N, usu prep N disapproval