Zeugma is the use of a word or phrase which appeals to two different senses. Sometimes the use of a zeugma only makes sense in regards to evoking one sense although it is applied to two.
An example of a zeugma is (as given by Merriam-Webster):
She opened the door and her heart to the boy.
An example of a zeugma in "The Scarlet Ibis" is as follows:
"Don't leave me, Brother! Don't leave me!"
Doodle, after Brother shows him the coffin their father built for Doodle, cries out to his brother not to leave him. This phrase has two very specific meanings. First, Doodle is afraid that Brother will die and leave him. Second, Doodle is afraid that Brother will leave him alone (for the time being- not for good). The zeugma is repeated throughout the story so as to make it into a true zeugma. While the words mean one thing at one specific time, they change throughout the story.
Doodle is fearful that his brother will leave him behind when leaving for a short period of time and is fearful that his brother will die and leave him for good.