So if you're: poor, fat, older than about 35y or dare to wear; leggings, tunics, ankle boots, waterfall cardigans (or any cardigan whatsoever), floral dresses, wrap dresses, mixed patterns, dark socks with lighter footwear, oversized clothing (if old and/or fat), 'mountain' wear (AKA outerwear), long puffer coats, court shoes, ill-fitting clothes,
Or if you wear clothing from: FatFace, Seasalt, White Stuff, Boden, Joules, Mountain Warehouse, Fly, Irregular Choice etc..
Ultimately, in order to avoid being frumpy, you must only shop in:
Zara, Cos or Whistles
You must only wear and present as:
Tailored, flattering clothing (and by flattering, it means don't be fat, old, short or without make-up). You must have regular haircuts, manicures, pedicures and maintain the utmost personal grooming practices.
You must never wear 'inappropriate' clothing at any time, e.g. never wear a 'ski' coat if you're not actually on a mountain.
So, as long as we can all remain under 35, wealthy, thin, tall and primp and groom ourselves, we MIGHT escape the Mumsnet frumpy label.
Easy.