JM2C:
To me, the term "technical diving" has a very precise meaning in SCUBA. Technical diving is: Any and all diving beyond "Recreational Limits." Now we ask what are "Recreational Limits?" There is a pointless conversation about all non-professional diving being recreational. Luckily for us, we understand that in English, the word "recreational" means one thing in one context, and another thing in a different context. The term "recreational limits" refers to a fairly well-understood set of activities deemed reasonably safe for divers trained by the big agencies. We can figure out what these activities are by looking at the agencies's training curricula. Anything an agency trains a recreational diver to do is a within recreational limits.
For example, everything you can take from PADI, including the specialties, is still recreational diving. Advanced recreational diving perhaps, but within recreational limits. Note that I am not saying that a PADI OW diver is trained to dive within recreational limits. For example, PADI's own guidelines are that an OW diver is supposed to stay above 60' until trained with Deep Specialty or AOW. So a 90' dive can be within recreational limits but be beyond the training for many recreational divers.
"Recreational limits" include obvious things like so-called no-decompression diving and no-overhead diving. PADI does provide for the option of limited wreck penetration in the presence of an instructor when you take the Wreck Specialty. Therefore I conclude that there are some limited cases where a wreck penetration falls under the umbrella of diving within recreational limits.
So now I return to my own personal definition of technical diving: Any dive falling outside of the training designated by a major agency as being within "recreational limits." This in no way suggests that technical diving is a precise activity. This in no way suggests that technical diving is not recreational in nature. This in no way suggests that the agencies have sound or sensible definitions of what is and isn't within recreational limits, or that they agree with each other. And I am not saying I believe that PADI training or anything else is a sound approach to risk management. Just that it provides a fairly clear criterion for distinguishing recreational diving from non-recreational diving, and that I am comfortable using the word "technical" to describe diving beyond recreational limits.
p.s. This definition can also be used to answer the gear debate. Is BP/W and long hose technical even on a shallow, OW dive? Good question. Can you find a PADI class where they will teach you to use them? Likewise with doubles: Will an instructor teach you how to shut down a free flowing post and/or isolate them as part of your deep or ice specialties? If so, doubles are not technical in and of themselves. What about reels and line handling? Well, do you learn those in your PADI Cavern Specialty? Yes? Than a reel is not in and of itself technical. Simple!
So... When you see me with BP/W, long hose, single tank with Y valve, and a reel hanging from my waist, you will know that I am not a technical diver, just a recreational diver diving within recreational limits.