洞子

dòngzi
  1. cave
  2. pit
  3. (coll.) greenhouse

CEDICT

colloquial

Entry Composition

1 洞 dòng
  1. cave
  2. hole
  3. zero (unambiguous spoken form when spelling out numbers)

classifier: 個
2 子 zi noun suffix, as in 椅子 yǐzi "chair"