I am reading the following document of Solitary waves page $14$. And I found the following symbol $\doteqdot$.
What does $\doteqdot$ mean? For example: $$y_t \doteqdot -c_0y_x $$
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After the very first equation (1.1) is this line
breaking occurs for a≑d. ...
so I think that it means "approximately equal to" which is usually written with ≈. I don't know why the author decided to use this symbol. It must be a rare usage because I had not seen it used before.
Search "Geometrically equal to" on this page
I don't know what that means, but it's the right symbol.