Thanks for the added link! Question is: What term is more common? I don't have ten diamonds at home, so I can't tell :)
If I understand it correctly, some may call it "trillion" even if it's a "Triangel" (see your link), so you may be right back where you started.
To explain what I mean:
"There are many ways to draw a triangle, and there are many ways to craft a triangle cut diamond. There are also many names the triangle shaped diamonds appear under in the marketplace: trillion, trilliant, and trillium – all of which describe a diamond cut in a shape of a triangle."
http://guide.diamondpriceguru.com/diamond-and-ring-basics/di...Or:
"Phantasieschliff beim Diamant = Diamant-Triangelschliff. Besitzt eine dreieckige Tafel, um die sich drei parallele Reihen von treppenförmigen Facetten anschließen."
http://www.beyars.com/lexikon/lexikon_1104.htmlDoesn't seem to match, does it?