Why is “bat down” not listed in any of major English dictionaries as an idiom, set phrase, collocation, no matter whatever it is?

I came across the following passage in September 17 “The Hill.” under the headline, “Trump says Kavanaugh may be delayed.”:

“If it takes a little delay it’ll take a little delay.” Trump told reporters at the White House. "I’m sure it will work out very well.” Trump batted down a reporter who asked if Kavanaugh should withdraw, calling it a “ridiculous question.”

I took “bat down” as “snub” or “shut out,” and consulted online dictionaries to make it sure, and found none of them including Oxford, Cambridge, and Collins Cobuild listed “bat down,” though they list “beat down,” “pat down,” “sat down,” and you can name it.

An online English / French dictionary translates “bat down” as “dėmolir.”

Google N gram shows that the use of “bat down” started in mid 19 century. It soared up in mid 20 century, dropped once, and regaining currency since 1990s.

I wonder exact meaning of “bat down,” and why the phrase is not shown in major dictionaries.

Addendum:

With JJJ’s edit, I’m a bit surprised to find the quoted paragraph was rewriten by the author in the latest version of the Hill, It goes now:

“When asked if Kavanaugh should withdraw, Trump said it was a “ridiculous question” but added that he has not spoken with the federal judge about the accusations. The phrase, “batted down” has gone.

I wonder why the author reworded the line in question and if he thought the use of “batted down” awkward or unsuitable to the context. What is your take on this rephrasing?

Solution 1:

The expression doesn't come from baseball, but from the more general sense of "strike with a baton". When you "bat" something, you hit it with the palm of your hand, and generally without much concern where it goes, so long as it goes away from you.

If a question is "batted away" or "batted down", it is dismissed without much concern, or much grace.

Solution 2:

I think the real answer is that "bat down" is not listed as an idiom because it is a natural figurative phrase that uses the first verbal sense of bat defined in the OED:

To strike with, or as with, a bat; to cudgel, thrash, beat.

Because the word "bat" can be replaced with synonyms, the phrase functions more as a metaphor than an idiom.

Trump batted down a reporter['s question].

Trump swatted down a reporter['s question].

Trump struck down a reporter['s question].

If to bat down was an idiom, it would come with a bundle of synonymic idioms as shown above. Instead, any could be considered a figurative metaphor for dismissing the reporter's question.

Trump dismissed a reporter['s question].

Solution 3:

the closest sounding idiom is batten down the hatches, but with an entirely different meaning. TFD

To bat down is not idiomatic ... it simply means to knock someone or something down as if with a bat, and in Trump's case it is figuratively done.

As in:

Trump dismissed/ knocked down (fig.) a reporter who asked if Kavanaugh should withdraw, calling it a “ridiculous question.”