Great post
@Bob Barnes! I think starting by defining some freestyle vocabulary is a great way to get the ball rolling here. Although I probably should start by saying that there is now a distinction in the industry between "freestyle" and "freeride". Freestyle generally refers to competitive moguls, while freeride encompasses park, pipe, and big mountain. When I started the thread, I used "freestyle" because I assumed it would resonate a little stronger with the crowd here. But generally speaking, the skiing I participate in, coach, and will most likely be discussing here falls into the realm of "freeride".
I'm obviously not going to sit here and define every single trick out there, as there are probably hundreds, if not thousands of variations. But I will attempt to describe all of the fundamental tricks upon which all others have evolved. Lets get started!
When I begin to teach someone who is new to the freeride world, I break down tricks into three basic categories; spins, flips, and grabs. Spins should be pretty self explanatory. They are horizontal or x-axis rotations that generally increase by 180* (i.e. 180s, 360s, 540s, 720s, 900s, 1080s, etc.). The only caveat here is that spins can be off-axis, meaning that the skier's body does not necessarily need to be straight up and down (think helicopters back in the day). Today, we often do off-axis spins which fall into two categories; cork and bio. A cork spin is an off-axis spin where the skier's upper body leans back towards the takeoff of the jump, while a bio is an off-axis spin where the skier's upper body leans forward towards the landing of the jump. These off-axis spins have become much more common today than straight spins.
Now an off-axis rotation is only a spin so long as the skier's feet do not travel above his or her head. The second that begins to happen we are now doing an inverted aerial, which leads us to our flip category. Flips are vertical or y-axis rotations in which the skiers feet travel over his or her head. Backflips, frontflips, and sideflips are probably the most familiar to most. But this concept of off-axis rotations applies to flipping as well. Flat spins, misty flips, rodeos, and D-spins, are all types of flips (trick names can be somewhat misleading, probably because they were invented by kids). Bob had mentioned a D-spin in his post so lets start there. A D-spin, named after Mike Douglas, is essentially a back full, or a backflip 360. It is called a spin, but the second the skier's feet travel over his head, it is technically a flip. Now if anyone recalls the 2002 Winter Olympics, you may remember when Jonny Moseley debuted the "dinner roll". At the time, FIS prohibited inverted aerials in competition. Moseley was attempting to get around this rule by turning the inverted D-spin, into an actual spin. The "dinner roll" name never really caught on in the freeski community. We now refer to this trick simply as a cork 720; two off-axis rotations in which the skier's feet never travel above his head.
A flat spin (again another misnomer), is actually a flip. It is essentially an off-axis backflip where the skiers feet travel over one shoulder, rather than directly over the head. A flat spin develops into a rodeo as the skier begins to add more spin to this flip. I think this may be a difficult concept to explain in words, so I will eventually get around to posting some videos that demonstrate some of these subtle differences. But for now, think of rodeos as an off-axis backflip with a spin.
Finally the misty flip. This trick is essentially the opposite of a rodeo; it is an off-axis frontflip with a spin. Again, I will post videos for clarification.
Moving on to grabs. A grab is anytime the skier physically touches one or both of their skis with their hand. There are so many grab variations that it would be futile to attempt to describe all of them here. Perhaps we can do a "grab of the day" type thread where I introduce and describe a new grab each day! But Bob had mentioned a mute grab, so I will start there. A mute grab is a classic that we have all seen at some point. Jonny Moseley may have really put this one on the map when he introduced the mogul community to the 360 mute in the 1998 Winter Olympics. A mute grab involves reaching across the body and grabbing the outside edge of your ski. For example, I can reach with my right hand and grab my left ski. When I say outside edge, I simply mean the edge that is furthest from my hand (not to be confused with inside and outside as it refers to turning). This is important to understand because the world of grabs is riddled with subtle nuances and variations. If I were to reach with my right hand and grab the "inside edge" (i.e. the closer edge) of my left ski, I would be doing a critical, not a mute.
I'm going to finish up here with a very quick explanation of switch skiing. "Switch" refers to skiing backwards. I can takeoff a jump switch or I can land a trick switch. Or I can takeoff and land switch, like when I'm doing a switch 360 or switch 720. In a later discussion, I will attempt to explain how taking off switch can fundamentally change our understanding of certain off-axis rotations. For example, the motion I use to do a misty flip is the same motion I use to do a switch rodeo. The reason is because these tricks are essentially opposites of one another. When I turn around and do a misty flip backwards, I am now doing a rodeo. Make sense?? Believe me, I do this stuff everyday and I'm sometimes confused about certain tricks.
Anyway, I hope that helps to clarify a few things and I hope that it can help contribute to a substantive conversation about this stuff. I've tried to post these types of threads elsewhere and they are often shutdown or lose momentum. Please post any questions you may have as I'm sure my abbreviated description of this stuff has left many of you more confused than before!