Definitions of yawning:

• noun:   an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom

  Example: "The yawning in the audience told him it was time to stop"

• adjective:   gaping open as if threatening to engulf someone or something

  Example: "The yawning mine shaft"

• adjective:   with the mouth wide open indicating boredom or sleepiness

  Example: "A yawning congregation"