intransitive verb
Definition: To open your mouth wide and take a deep breath, often because you are tired or bored.
Example: She couldn't help but yawn during the long lecture.
noun
Definition: An act of opening the mouth wide and taking a deep breath, usually because of tiredness or boredom.
Example: After staying up late, I couldn't help but let out a big yawn during the meeting.
transitive verb
Definition: To open one's mouth wide and take a deep breath, often because one is tired or bored, or to express a lack of interest.
Example: She couldn't help but yawn during the long lecture.