what does "frames with intermittent jank" means in Chrome DevTools docs?

Question

I got confused when I read Chrome DevTools |Timeline.

Keep in mind that just tracking the FPS counter may lead to you not noticing frames with intermittent jank. Be careful when using the content. It is also worth noting that FPS on desktop does not equal FPS on devices and special care should be taken to profile the performance there too.

does frames with intermittent jank means the frame that fail to use real hardware frame?

Answer 1

Apparently "jank" is a neologism:

"Jank is any stuttering, juddering or just plain halting that users see when a site or app isn't keeping up with the refresh rate. Jank is the result of frames taking too long for a browser to make, and it negatively impacts your users and how they experience your site or app."

From http://jankfree.org/

So "frames with intermittent jank" means ... well ... intermittent jank.

does frames with intermittent jank means the frame that fail to use real hardware frame?

Nope. You can't make that inference.