Sentence:  One evening, when the Boy was going to bed, he couldn't find the china dog that always slept with him. Nana was in a hurry, and it was too much trouble to hunt for china dogs at bedtime, so she simply looked about her, and seeing that the toy cupboard door stood open, she made a <WSD>swoop</WSD>. 
Meaning of the word marked with <WSD> tags:  An instance, or the act of suddenly plunging downward.