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.
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)?