After Apple-Picking What is “rumbling”? What literary device is the word “rumbling”? Why does the speaker have to be careful with the apples? If an apple is bruised, what must be done?
In this poem, the speaker is tired after a long day of picking and processing apples. Some people see this as a metaphor -- they say that he has lived a long life and is now tired and ready for death.
As to your specific questions. The apples are rumbling as they get dumped down a chute into the cellar. The word "rumbling" is an onomatopoeia because it sounds like the action it represents.
It is important to be careful with the apples so that they do not get bruised. If they do get bruised, they become worth less. They can't be sold or used for most stuff -- they have to get pressed for cider.