non-verbal, non-speaking, silent, refraining from speaking or unable to speak; sometimes mute which can also be ableist; colloquially used to mean unintelligent or senseless
Dumb initially meant "mute, silent, refraining or unable to speak." Old German thumb carried a dual meaning of "stupid", which eventually took over.
An oft-cited quote by Greek philosopher Aristotle reads, "Men that are deaf are in all cases also dumb.**" Historically the Greeks valued physical prowess (as evidenced by their invention of the Olympic Games) and their language, so anyone who lacked the ability to perform certain physical tasks or conduct reason (verbalise reason, rather) in their language was considered invaluable to society. The historical context is still ever present today, where we devalue disabled bodies and minds.
Using dumb reinforces these cultural values.
**Isolation to only "men" also reinforces the historical patriarchical ideas that intersected with these ableist ones.
Using the word dumb reinforces the idea that Deaf and/or non-speaking/non-verbal people do not have valuable ideas to contribute, and that we only value people based on their idea to generate ideas and goods (see Ableism)
By using ableist language, we are perpetuating violence against people who experience mental or psychological disabilities. Using this language perpetuates those systems and language of harm, regardless of our intent.
Be more specific. Typically we can find an alternate definition by taking time to reflect on what emotion we're really feeling.