For those of us who aren't in the know, apparently FOUT stands for "Flash of Unstyled Text": https://css-tricks.com/fout-foit-foft/
If anyone wants to see an example of FOUT, you might be able to on my website with Chrome 50. I am currently experiencing this and then I found this bug report. Reload a few times if you don't see it at first.
edit: FOUT usually means a fallback font is briefly shown before flickering and rendering a loaded web font.
edit: As people have pointed out below, my situation likely has nothing to do with this possible bug. My website layout is very lightweight and Chrome is rendering it probably faster than the other browsers I tried which explains why I'm seeing FOUT more often in it. And yes, I'm loading my CSS asynchronously which is the main reason behind my FOUT.
However I'm not seeing FOUT on Safari for Mac and iOS and Firefox for Mac at the moment.
*edit: I definitely understand that you're right Paul. If the website loads slow, FOUT is expected. However, I'm seeing it more than what I expected to with loadCSS combined with this bug report I found. So I'm kind of leaning toward the idea that it is a bug in Chrome 50. If not, I'm wrong and it's only my loadCSS causing it.
Btw, once the CSS `font-display` property becomes available, you’ll be able to control web font rendering to some extent, but as of now, this type of FOUT is the best approach, since, if you went with FOIT, you’d risk up to 3 seconds of whitespace in case your fonts experienced network congestion.