Gape
Definition 1 of 4
Pro Tip 1/2
Shock or Surprise
Use 'gape' when someone is so astonished that they can't close their mouth. After the magic trick, we all gaped in disbelief.
Pro Tip 2/2
Motionless Staring
'Gape' often implies being so stunned that one forgets to move or react. He gaped at the sky where the UFO had disappeared.