play down

1.  Make little of, minimize the importance of, as in A skillful salesman plays down the drawbacks of the product and emphasizes its good features. [First half of 1900s]
2.  play down to. Lower one's standards to meet the demands of someone, as in Some stand-up comics deliberately play down to the vulgar taste of their audiences. [Late 1800s]

Definition: pretend like something is unimportant
Antonyms: blow up, build up, explode, play up

The verb has one meaning:

Meaning #1: understate the importance or quality of
  Synonyms: background, downplay
  Antonym: play up (meaning #1)