last-th conversion: switches the last terbri with the first one.
For exactly-n-terbri, this it the nth conversion. For a one-terbri word, this is equivalent to re'au'e. For two-terbri selbri, this is se. For three-terbri selbri, this is te. For four-terbri selbri, this is ve. For five-terbri selbri, this is xe. In general, this might be equivalent to sexiro, although this might be debatable. The meaning of the result in the context of its being applied to a selbri with opened-ended terbri structure (such as "jutsi") is yet to be explored.