Mutton Dressed As Lamb Meaning

(idiomatic, derogatory) A middle-aged or elderly woman dressed in a style more suited to a young woman, especially if in a deliberate attempt to appear young.

Example:   The teacher was trying to appeal to her students by wearing a short skirt and strappy top. In reality, she just looked like mutton dressed as lamb.
2003, Elizabeth W. Markson, Chapter Three: The Female Aging Body Through Film, Christopher A. Faircloth (editor), Aging Bodies: Images and Everyday Experience, page 85,
  In one of the rare cinematic depictions of an older woman as sexually attractive and active, Moreau also contributes to the end of Syl′s innocence by seducing him in the summer house. No mutton dressed as lamb could have done better!
2007, L. H. Maynard, M. P. N. Sims, Demon Eyes, Dorchester Publishing, New York, page 224,
  Elegant, slightly chic, but not mutton dressed as lamb. It was important to present a professional appearance to her former employer.
2009, Dr John Chibaya Mbuya, Bulelwa Muphela, Grooming and Ettiquette for Corporate Men and Women, unnumbered page,
  South African women are also so scared of looking like mutton dressed as lamb that we have plenty of women looking like lamb dressed as mutton!
2009, Jah Wobble, Memoirs of a Geezer: Music, Mayhem, Life, Serpent's Tail (Profile Books), UK, page 65,
  I thought that the American side of punk was generally full of mutton-dressed-as-lamb degenerates, most of whom were smack heads, who could do with acquainting themselves with a bit of soap and some hot water.