The phrase "third kit" refers to a special set of clothing or uniforms that a sports team wears during matches, typically when their regular home or away kits cannot be used. Full definition
Don't get why clubs need a whole new third kit just used last seasons away kit. (footballkitnews.com)
No, it's not a signing that we're bringing you today, instead we've got some of the best shots of our new third kit. (fresharsenal.com)
SEE MORE Arsenal transfer news (Images) REVEALED: New Arsenal third kit for cup competitions Premier League's richest owners: Arsenal, Chelsea, Liverpool and Manchester United's billionaire masters revealed (caughtoffside.com)