[SonOfLilit]

Apparently "onomatope" is a much less popular name for the same thing (e.g. Wikipedia uses my version).

I mean that the "remove a word" 'symbol' is a 'word' that represents the verb he was trying to invoke, by sounding like it.

Birds chirp, bees buzz, moderators, toilets flush.

[Gander5739]

Apologies if I'm being totally thick, but you're saying the lack of a word is acting as an onomatope (or an onomatopoeia if you prefer)?

[SonOfLilit]

Yes. You could say this is the sound of silence.