What does "stave" mean in the novel A Christmas Carol?

A stave is a chapter in A Christmas Carol.

If you look at the title of the book, you can see the significance of the chapters being called "staves."  Dickens is acting as if the book is a Christmas carol, and each chapter is part of the song.  Stave is another word for “staff.”  In music, a staff is how music is written.  It is the lines on which the notes are displayed.

Dickens could have just named his chapters as chapters, but what would be the fun of that?  By calling the chapters staves, Dickens reinforces the idea that the book is a song.  Songs are short, as this book is, and at the holidays carols often have deeper meanings.

The metaphor continues with Dickens’s use of other imagery.  You will notice as you read the book that Dickens is very descriptive, and loves to use similes, metaphors, and symbolism throughout the book.  Even Dickens’s note to the reader contains a metaphor.

I HAVE endeavoured in this Ghostly little book to raise the Ghost of an Idea, which shall not put my readers out of humour with themselves, with each other, with the season, or with me. May it haunt their houses pleasantly, and no one wish to lay it. (Note)

When Dickens says the book will “haunt” his readers’ houses, that is a metaphor for people bringing the book into their homes and making it a part of their holiday celebration.  Just look at the description of Scrooge, which is full of figurative language.

Oh! but he was a tight-fisted hand at the grindstone, Scrooge! a squeezing, wrenching, grasping, scraping, clutching, covetous old sinner! Hard and sharp as flint, from which no steel had ever struck out generous fire; secret, and self-contained, and solitary as an oyster. (Stave 1)

Scrooge is described as “a tight-fisted hand at the grindstone” even though he was a banker and did not use a grindstone.  This metaphor is coordinated with several similes, including “sharp as flint” and “solitary as an oyster.”  These descriptions add to the poetry of the book and reinforce the idea that it is like a song.

Dickens wanted to create a book that would help people celebrate the holidays, but would also be meaningful.  The lesson he wanted to teach his readers was that during the holiday time of year, it was their responsibility to look out for the less fortunate.  The book is so powerful that, like a Christmas carol, it is still loved by many around the world over a hundred years later.

What is a stave in Charles Dickens' A Christmas Carol?

The word stave has many different definitions. If used as a noun. stave refers to a wooden plank used in the construction of a building or a musical staff (symbol). If used as a verb, stave refers to breaking something by force or averting something negative. None of the previous definitions define stave's use in Charles Dickens' A Christmas Carol (although the musical staff is the closest). 

Dickens use of the word stave refers to chapters in the text. This is a common concept for him given that he uses similar musical terms for other texts ("quarters" in The Chimes and "chirps" in The Cricket on the Hearth). Here are the names of the five staves in the novella.

Stave I: Marley's Ghost

Stave II: The First of the three Spirits

Stave III: The Second of the Three Spirits

Stave IV: The Last of the Spirits

Stave V: The End of It

The use of the word stave here refers to songs (in order to make the reader more aware of the relevance of the title (Christmas Carol--in reference to songs sung at Christmas time). 

Why does Dickens use the term "stave" for his chapters in A Christmas Carol?

The term "stave" ("staff" in American English) refers to the set of five lines separated by four spaces within musical notation. Every line represents a different pitch in the music.

Dickens likely used the term "stave" instead of "chapter" as a way of tying into the title of the novella, A Christmas Carol. Each stave shows a new progression in Ebenezer Scrooge's moral awakening, just as different bars on a stave record different musical progressions. For example, the stave featuring the Ghost of Christmas Past is bittersweet, with Scrooge fondly remembering deceased loved ones and regretfully recalling bad decisions which gradually isolated him from other people, while the stave of the Ghost of Christmas Yet to Come is ominous and sinister, focusing on what will become of Scrooge should he continue to push others away and treat the less fortunate with ice-cold contempt.

Though every stave has a different emotional pitch, if you will, they all come to form one harmonious narrative, showing a man's movement from amoral miser willing to turn a blind eye to human suffering to a compassionate man who comes to embody the goodwill so often wished for during the Christmas season.

Does "stave" in A Christmas Carol have a double meaning, hinting at averted misery?

Good catch on the double meaning! Dickens was very intentional with his wording, so we have to assume that this was intended as well.

On the surface, we take the word "stave" at face value -- as a portion of a song (like a stanza of a poem).  This matches the title of the work.  If the entire work is a song or a "carol," then it would make sense that the individual parts that comprise it would be known as staves.

However, as you astutely point out, to stave something off is to keep something from happening, or to at least delay it.  No doubt the ghosts are trying to stave off Scrooge's potentially meaningless life by showing him his past, present, and future.