noun

• (historical) A piece of fur or cloth, usually with open ends, used for keeping the hands warm.
  "Selwyn, sitting up rumpled and cross-legged on the floor, after having boloed Drina to everybody's exquisite satisfaction, looked around at the sudden rustle of skirts to catch a glimpse of a vanishing figure—a glimmer of ruddy hair and the white curve of a youthful face, half-buried in a muff."
• (vulgar slang) The vulva or vagina; pubic hair around it.
  "."
• (synecdochically, vulgar slang) A woman or girl.
• (glassblowing) A blown cylinder of glass which is afterward flattened out to make a sheet.

noun

• (colloquial) A fool, a stupid or poor-spirited person.
  "Can you fancy that such an old creature (an old muff, as you call him, you wicked, satirical man!) could ever make en impression on my heart?"
• (slang, chiefly sports) An error, a mistake; a failure to hold a ball when once in the hands.

verb

• (sports) To drop or mishandle (the ball, a catch etc.); to play badly.

noun

• (slang) A muffin.
  "Skinny lattes and a couple of blueberry muffs."