Turn refers to high speed turn. Throw an overstable disc RHBH flat, and it will go straight for a while, and fade left. Throw an understable disc RHBH flat, and
if you get it up to speed, it will actually turn to the right. Depending on the disc, how hard it was thrown, and perhaps most importantly,
one's techniques technique (or lack thereof), it might fade back to the left as it slows (S-shot) or it could hold the line and continue it's glide to the right.
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That is high speed turn or what people refer to as a disc "turning over." A flight that starts out straight, but then turns to the right for RHBH, or to the left for RHFH, in opposite of the direction which it will fade when it slows down. If your a lefty, just switch things like a mirror image.
Flipping refers to the hyzer flip. So you know that hyzer means throwing the disc with the outside edge angled downward, rather than flat. With a disc that's stable or neutral, it will hold that hyzer line throughout the flight. If you throw a understable disc on a hyzer line
with sufficient velocity,
it will not hold a hyzer line. In the example above, the disc turned over. On a hyzer flip, the disc must first "flip" up to horizontal from the hyzer angle it was thrown on. Depending on the disc's stability and velocity, it might continue to "flip" and turn to the right (as above) or it may only flip up to flat, and continue to go straight until it slows and fades back to the left.
All discs break in and lose some stability with time and punishment. Once they've lost a good deal of their original stability when new, people refer to them as "flippy." Keep in mind that flippy is relative to the disc's original stability. A "flippy" Firebird or Predator may have lost a great deal of its original stability, but since they're so overstable to begin with, they still probably aren't truly understable.
Hope that helps.
There! Was I nice enough?