Never heard of "Referee Technical Decision", don't know if Wikipedia is reliable in this case. It's "RTD" for "retired". As already mentioned. Also, I seen some older record books use "ret." instead. "RSC" and "RSF" also used to be common, meaning "referee stopped contest" or "referee stopped fight" .... which is same as TKO .... and "retired" is often recorded as TKO too of course.