Sentence:  At length, quite exhausted by the attempt to be amused with her own book, which she had only chosen because it was the second volume of his, she gave a great <WSD>yawn</WSD> and said, “How pleasant it is to spend an evening in this way! ...” 
Meaning of the word marked with <WSD> tags:  The action of yawning; opening the mouth widely and taking a long, rather deep breath, often because one is tired or bored.