A verb appearing as G. crista- “slash, cut, slice” in the Gnomish Lexicon of the 1910s, related to G. criss “cleft, gash, gully” (QL/47) and clearly based on the early root ᴱ√KIRISI (QL/47).

Neo-Sindarin: Since both S. criss “cleft” and the root ᴹ√KIRIS survived in Tolkien’s later writings, I think ᴺS. crista- “to slash, cut, slice” can be retained for purposes of Neo-Sindarin. I would further assume it is a larger or more violent cut than rista- “cut”.