Center letter: r
Outer letter: b f g l o u
Answers (28):
  bullfrog
  blur
  blurb
  boor
  bulgur
  burb
  burg
  burgoo
  burl
  burr
  burro
  floor
  flour
  forgo
  four
  frog
  froufrou
  frug
  furl
  furor
  grog
  grub
  gruff
  guru
  logroll
  roll
  roof
  ruff