x1 is a grandparent of x2 by bond/tie/relation/standard x3 (not necessarily genetic/biological nor necessarily directly ancestral); x1 is an associated member of x2's parent(s)'s parent(s)'s generation.
No prefix "great-"s may immediately precede the English translation of this word when the root is "grandparent"/"grandchild" or the like (due to slippage of clarity in reference to the pertinent generation); furthermore, it must refer to that generation (so no additional "great-"s may immediately precede the English translation of this word when it means "great-uncle"/"great-aunt" or the reciprocal relationships, and it cannot refer to uncles, aunts, nieces, or nephews). Might apply to great-aunts and great-uncles; it does not in any way intersect with the reference set of "famti" in a simple family/tree. See also: tcuti, which specifically excludes the potential meaning of grandparent/grandchild and which specifically includes the meaning of aunt/uncle/nephew/niece and higher generational separations too (such as great-great-uncle vel sim., unlike this word which is restricted to the grandparents' generation); riryrirni (or the like), which excludes the potential meaning of great-uncle/great-aunt or the reciprocal relationships. See also: "dzena" (which is more general and not necessarily familial by any given standard).