Often used in fashion blogs. Used to describe an outfit that is too coordinated and consists of too many of the same types of colours, patterns, fabrics, accessories, designer pieces, thematic elements, etc. Can also be used in reference to interior design.
FabSugar on Kate Hudson's all grey outfit: "Before this, I didn't know there were degrees of being matchy matchy."

or

A: How do I look?
B: Too matchy matchy, try a different sweater.
by L. Alice December 11, 2007
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Matchy matchy is when a group of people or friends wear similar clothing maybe same colors etc. (matching), found by Greek trapers: Snik, gameboy!
- What is your gang wearing?
- We’re always matchy matchy we all wear the same.
by thatantony January 31, 2023
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