yawning
n. uncountable B1 Intermediate US //ˈjɔnɪŋ// UK //jˈɔːnɪŋ// yawn·ing
n. the act of opening your mouth wide and taking a deep breath because you are tired or bored. It is something your body does automatically.
n. an involuntary intake of breath through a wide-open mouth, typically triggered by fatigue, boredom, or drowsiness.
He tried to hide his yawning during the long meeting.
The sound of someone yawning in the quiet library seemed to trigger a chain reaction among the other students.
Scientists have long debated the physiological purpose of yawning, with theories ranging from brain cooling to a primitive form of social communication within a group.
Usage
Often used as an uncountable noun to describe the general action, though 'a yawn' is the preferred countable form for a single instance.