汗如雨下

hànrúyǔxià
  1. sweating like rain (idiom); to perspire profusely
  2. sweating like a pig

CEDICT

to sweat buckets; to sweat profusely

Wiktionary

汗水很多，如下雨一般。

重編國語辭典

Entry Composition

1 汗 hàn
  1. perspiration
  2. sweat
  3. to be speechless (out of helplessness, embarrassment etc) (Internet slang used as an interjection)

classifiers: 滴, 頭, 身
2 如雨 rúyǔ
  1. (literary) like rain; in large amounts
  2. like rain; in large amounts
3 下 xià
  1. down
  2. downwards
  3. below
  4. lower
  5. later
  6. next (week etc)
  7. second (of two parts)
  8. to decline
  9. to go down
  10. to arrive at (a decision, conclusion etc)
  11. measure word to show the frequency of an action