Anyone racing outside the elite field, scored within their age category. Age-groupers almost always race under different bike rules than the elites you see on TV.
The word isn't a polite substitute for amateur — it decides which rulebook applies to you. Elite racing at the Olympics, the World Cup and the World Triathlon Championship Series is draft-legal; age-group races are almost always solo time trials with no drafting. Carry the TV picture over to your own race day and you collect time penalties. The second effect matters just as much: age-grouper sets your benchmark. Over the Olympic distance the average across all age groups is around 2:53 hours, while the men's elite winner in Paris 2024 came through in 1:43:33 — measuring yourself against that number is the fastest way to lose motivation. What often gets missed: World Triathlon crowns its own age-group world champions per age category, with qualification running through national federations and differing by country. That's a reachable goal, not an elite privilege.