Center letter: r
Outer letter: b c i o p t
Answers (39):
  probiotic
  boor
  boric
  brio
  cirri
  citric
  coir
  crib
  critic
  croc
  croci
  crop
  orbit
  poor
  port
  portico
  prior
  proctor
  prop
  ribbit
  riot
  robot
  robotic
  rococo
  root
  roti
  rotor
  tori
  toric
  torii
  toro
  torpor
  tort
  tricot
  trio
  trip
  troop
  tropic
  trot