一下

yīxià
  1. (after a verb) a bit; a little (indicating brief duration, or softening the tone, or suggesting giving sth a try)
  2. all at once; suddenly

CEDICT

Entry Composition

1 一 yī
  1. one
  2. single
  3. a (article)
  4. as soon as
  5. entire; whole; all; throughout
  6. "one" radical in Chinese characters (Kangxi radical 1)
  7. also pr. yāo for greater clarity when spelling out numbers digit by digit
2 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