A hypothetical 400-page bill is brought forward in Congress, and voting on the bill is expected to happen in only one hour. Legislators don’t have enough time to read and absorb the entire thing, so they scan through it quickly, looking for specific phrases and keywords just to get the gist of what it’s all about.
Are these legislators rifling through the bill, or are they riffling through it? Both words can indicate quickly going through something, but the difference between them can be vast.
To rifle (with a long i) means to search hastily and haphazardly, often with the intent to steal. A burglar might rifle through a victim’s chest of drawers in search of valuables, for example. Copyeditors are more likely to rifle through a reference work or an index, not to steal but to verify a fact or find an earlier use of a word or phrase in order to impose consistency on the text.
In this example from The Observer, the writer manages to use rifle as both a noun and a verb:
Five police officers, one armed with an assault rifle, ask him to remove its contents, and two female passengers dressed in leggings and flip-flops duly unload the bulging plastic bags inside and watch with increasing irritation as the police rifle through their contents.
To riffle (with a short i) is to flip through cursorily, and specifically, according to Merriam-Webster, “to leaf by sliding a thumb along the edge of the leaves.” You can make a fun noise and generate a small breeze by riffling the pages of a book.
From M.R. Carey’s The Boy on the Bridge, an example with both rifle and riffle:
Then he squats, sets down his rifle and picks up the book, riffling the pages with his thumb.
So both rifle and riffle can indicate moving through the pages of a book, magazine, or other manuscript hastily. You might riffle through the dictionary, keeping an eye on the guide words at the top until you find the page you need. Or you might rifle through the dictionary in search of dog breed names.
Examples of misuse are legion, especially using riffling where rifling is called for. So keep an eye on these words, not only because the spell-checker won’t flag problems, but because there are plenty of instances in which either word could fit a sentence but yield different meanings.
Returning to the legislative bill example from the beginning, to say that legislators barely had time to rifle through the bill before voting on it would be much different than saying they barely had time to riffle through it. In the former, they had some time to scan through the pages; in the latter, they had no time at all, because it takes only moments to riffle through a stack of 400 pages.
Remember, as a general rule, that if the object of your attention is some sort of manuscript, riffling is something you do with the pages, but rifling is something you do with the text.