无底洞 (wú dǐ dòng) — bottomless pit (literal or figurative); a black hole (for money, resources, etc.)

Definition

Examples

• 这个项目就是个无底洞，投多少都不够。
  Zhè ge xiàng mù jiù shì gè wú dǐ dòng, tóu duō shǎo dōu bú gòu.
  This project is just a bottomless pit; no matter how much you invest, it's never enough.
• 家里的开销简直是个无底洞，永远填不满。
  Jiā lǐ de kāi xiāo jiǎn zhí shì gè wú dǐ dòng, yǒng yuǎn tián bù mǎn.
  Household expenses are practically a bottomless pit; they can never be filled.
• 他对新手机的需求就是个无底洞，永远嫌不够。
  Tā duì xīn shǒu jī de xū qiú jiù shì gè wú dǐ dòng, yǒng yuǎn xián bú gòu.
  His demand for new phones is like a bottomless pit; he always complains it's not enough.