This is the word to describe a woman who is kind of frumpy, but still "do-able". You may say your best-friends mother is a bit Frumpcious.
Frumpcious could also be used to describe any famously stern, older lady, with whom you would like to have a poke of.
Bernard - Your Mum's quite Frumpcious when she's mad. She gets a glint in her eyes, the kind of glint that makes you know that she's a go-er in the bedroom. Your Dad's a lucky guy!
Thomas - Errr, thanks, I guess!!
Paddy - For some strange reason, I can't quite put my finger on, I find Ann Widdecombe very Frumpcious. I'd love her to spank me silly with a Riding Crop.
Oliver - Yes, I know what you mean, I often have the same thoughts about Queen Elizabeth II. She has that Frumpciously stern glare, that gets me all excited in my pants.