So I don't know exactly what to call it - hence my search has come up short.

I'm still learning and improving my casting, settings, matching lines and all that - but I notice every so often I'll go to cast a bit further and while the spool is running it almost "loosens", not quite a birds nest, but then seems to tighten right back up to normal by the time the bait hits the water.

I'm concerned because I know something isn't right but I have no clue as it comes back to 'normal'.

Sounds like you're dialed in just about perfectly.

It sounds like the braking system is working as intended. No bird nesting means a successful cast so I doubt I'd really worry about it. I've never really watched my spool while casting as my thumb is usually blocking the view.

huh - I guess you may be right. I noticed it and just assumed something was off.

 

Well that's a relief! Thanks Choporoz and Kenmitch!

Like @Choporoz said, it sounds like you are right where you want to be. Almost backlashing means you have everything dialed to stop an actual backlash but you are on the edge so you are maximizing your cast. I'd just be careful if you are fishing in wind though because an "almost" backlash in one direction can be a real mess in another if you don't adjust the reel or use your thumb enough. 

55 minutes ago, walpy said:

I'm concerned because I know something isn't right but I have no clue as it comes back to 'normal'.

Yeah, you're casting too hard.  Either turn up the brakes a touch, or feather the spool with your thumb.

That's what my reels do when they are set just right for long casts with lighter lures, like living on the edge. I either feather with the thumb, or raise the rod tip at the end of the cast to speed up the spool a bit, and snap it shut while it's still paying out, (cause the quicker this one breaks (or is it brakes) the quicker I get a new one)). 

I call it "fluffing" because the lines lifts (putting space between layers) in the middle of the cast.  (Like fluffing a pillow.)  If it were that way at the end of a cast I would call it "overrun".....loose coils, but no backlash.

I dont know about the new high tech reels, but on my old Abu reels, I tend to touch the edge of my thumb on the spool and not sitting on top of the line. With your thumb on top of the line windings, seems easier to get the line loose or a backlash.