What does TMO stand for in rugby union officiating?

In rugby union officiating, TMO stands for Television Match Official.

The TMO is an off-field official who reviews video footage to assist the referee with specified decisions. The official works with broadcast replays and communicates with the referee, who remains the person responsible for the final ruling on the field.

Video review is especially important for grounding a possible try, identifying dangerous foul play, and checking whether an infringement occurred immediately before a scoring event. The review process is intended to correct clear errors without turning every passage of play into a prolonged investigation.

The TMO is sometimes casually called the video referee, but Television Match Official is the formal rugby term. Rugby league also uses video officials, although its protocols and terminology are governed by a different code.