Looking for a term to describe unusual openings in chess960 (you might be asking, 'Aren't they all unusual?'), I searched on various expressions that describe these openings in traditional chess. Here's what I found.
- 2,910 for chess "irregular openings"
- 2,420 for chess "unorthodox openings"
- 1,390 for chess "offbeat openings"
- 1,270 for chess "unusual openings"
- 153 for chess "strange openings"
- 71 for chess "curious openings"
The most used phrase was a variation of one of those above. It exceeds the combined count of all the above, a phenomenon for which I have no explanation (*).
I wanted my phrase to include openings like gambits. These are usually not included in any of the above, unless they are openings like the Halloween Gambit (1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Nxe5), which might also be considered for the following list.
Then the phrase I was looking for popped into my head. It encompasses all of the above, and then some. Most importantly, it's not in widespread use.
From Merriam-Webster.com extravagant:
1 a obsolete : strange, curious; b archaic : wandering
2 a : exceeding the limits of reason or necessity (extravagant claims); b : lacking in moderation, balance, and restraint (extravagant praise); c : extremely or excessively elaborate (an extravagant display)
3 a : spending much more than necessary (has always been extravagant with her money); b : profuse, lavish
4 : extremely or unreasonably high in price (an extravagant purchase)
Yes, that's exactly what I was looking for: Extravagant Openings! Any one of those definitions could serve the purpose I have in mind.
(*): Re 'a phenomenon for which I have no explanation', it seems to be caused by a Google idiosyncrasy: 'In order to show you the most relevant results, we have omitted some entries very similar to [those] already displayed.' This line of thought led to another candidate...
...which I'll save for another time.
Later: I received another suggestion via email; 'Since traditional chess has been depicted as a refuge for the logical mind, may I suggest MIND-BLOWING Openings, which would certainly cover most of my preferences.' As you can see in the stats...
...it's not in widespread usage.
Even Later: Two more terms are...