x1 ("ra'oi"-quote) is a long (unreduced) rafsi/combining form of word/concept x2 in language x3.
In Lojban, these exist only for gismu and maybe zi'evla and are the four- or five-letter rafsi (where the final "-y" is not counted as a letter in the four-letter case, and may or may not be considered to be part of the rafsi itself). Compare: "2 in language x3.">cmarafsi".