What is the word for making a point by saying nothing?

Instead of commenting on what he regarded as a ridiculous proposal he conveyed his disapproval by saying nothing at all. This is an example of xxxxxx.

Solution 1:

A single-word answer to fit ‘This is an example of...’ still seems elusive, but I have a couple of brief suggestion and one rather longer one, one of which might suit your purpose.

Depending on the context of your writing, it might be appropriate to say that He disdained to answer. In fact, Merriam-Webster specifically uses the example ‘disdained to answer their questions’ in its definition of disdain.

With a slightly more judgmental sense, you might also consider He scorned to answer.

(And, on reflection, you could truthfully say of his action/conduct, ‘This is an example of disdain/scorn,’ although of a very specific type. Perhaps it would suit your purposes simply to report the question, followed by ‘his silent disdain’ or ‘his disdainful silence’.)

I’ll mention a longer possibility because it seems suggestive. It seems to me that the common expression for what you describe is He refused [or disdained] to dignify the question with an answer. I can't help wondering whether, in a language where that expression is so current, a one-word equivalent might not exist.

Solution 2:

This is an example of: silence speaking volumes.

silence speaks volumes.

Silence can mean many things in interpersonal relationships. It's ambiguous. It can express lots of different emotions ranging from joy, happiness, grief, embarrassment to anger, denial, fear, withdrawal of acceptance or love.

google: silence speaks volumes meaning

Solution 3:

stonewalling (noun):

an act of delaying or obstructing a person, request or process

to stonewall (verb):

delay or obstruct (a request, process or person) by refusing to answer questions or by being evasive

'When she confronted Don, he stonewalled her and limited her access to the business records.'

'she has also stonewalled queries about her love life'

Source: ODO

Merriam Webster's Dictionary of Allusions details the etymology of 'stonewall' in US politics.

Solution 4:

To the extent that Wiktionary’s entry for “dismissiveness" includes the notion of “passively showing indifference or disregard” (as well as that of “actively dismissing or rejecting ideas or evidence"), you could interpret “passively” to mean/include “silently” or “by/with silence” and perhaps use that single word to say that:
“This is an example of dismissiveness.”

Personally, however, I would stretch it to two words to clarify that the disregard/disapproval was shown by/with silence alone (i.e., not accompanied with a dismissive facial/hand/eye-rolling gesture) and say that:
“This is an example of dismissive silence.”

(example use of “dismissive silence” from ‘The Poetics of Consent: Collective Decision Making and the Iliad’ by David F. Elmer, via ‘Google Books’)

(for three more examples of “dismissive silence,” please see pages 16 and 20 of Patricia Olivia Covarrubias’ article ‘Masked Silence Sequences: Hearing Discrimination in the College Classroom’ found on the University of New Mexico/Dept. of Communication and Journalism’s website here.