Mandarin: Cha Chui, Cha Chuey
Cantonese: Tsaab Tsui, Tsahp Tchoy
Yes, it is a 7* form, although it comes from Chang Chuan (longfist style) - (as does Syh Lo Bun Da - four direction fist - also incl. in the 7* style), and "is considered a powerful fist-set". It may also be included in other Mantis systems, but I don't know for sure.
I have heard it translated as "Piercing Strike", "Dagger Fist Hand", "Stabbing Fist Form", etc. - but I like "Fist of Penetrating Hammer" the best
There is also a 'ling' version - a two-man sparring set, and possibly a 'folded' set - but I'm not sure about that one.
Here is a link to a photo-set of this form, although I've noticed some slight variations in the way it's done compared to how I learned it...there's a lot of jumping and deep stances - very good leg workout...trust me
http://www.northernmantis.com/tsahpchoy.html