What is Steam's "download now" icon?
In the Steam client application there is a download now icon, here it is with hover over:
and by itself:
What is this icon?
It kind of looks like this Chinese character 不 but it wouldn't really make any sense why that would be the icon for download now.
The intent of the button is "Move to top of queue". It's an arrow pointing up, indicating that it's moving the selected item up, and terminating at a horizontal line which indicates the top bound of the queue.