堵

dǔ
  1. to block up (a road, pipe etc)
  2. to stop up (a hole)
  3. (fig.) (of a person) choked up with anxiety or stress
  4. wall (literary)
  5. (classifier for walls)

CEDICT

literary

Classifier for

牆 qiáng (slang) to block (a website) (usu. in the passive: 被牆 bèiqiáng)

classifiers: 面, 堵