stablemate

stable companion noun a horse stabled with another or one of several horses owned by the same person
Found on https://www.encyclo.co.uk/local/20974

Stablemate

Fighters who train at the same gym or under the banner of the same promoter.
Found on https://www.predictem.com/boxing/boxing-terms-lingo-jargon/

Stablemate

When two fighters train in the same gym, fight for the same manager or promoter, they are oftentimes called stablemates.
Found on https://www.titleboxing.com/boxing-dictionary

stablemate

[n] - a horse stabled with another or one of several horses owned by the same person
Found on http://www.webdictionary.co.uk/definition.php?query=stablemate
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