Center letter: p
Outer letter: c g i n o u
Answers (39):
  couponing
  pouncing
  cioppino
  coop
  cooping
  coping
  copping
  coup
  coupon
  cupping
  goop
  nipping
  opining
  opinion
  oppugn
  oppugning
  picnic
  pigging
  ping
  pinging
  pining
  pinion
  pinioning
  pinning
  pinup
  piping
  pippin
  pogo
  pogoing
  pong
  poop
  pooping
  popgun
  popping
  punning
  unpin
  unpinning
  upon
  upping