Here’s a question that I didn’t know the answer to for quite a while. Definitely not until after I graduated from college. (This is the sort of revelation that sets off a chorus of tut-tutting from the grammar police about the miserable state of our modern schooling.) When do I use flout and when do I use flaunt? Well, that I could answer. But I couldn’t answer the question of when I ought to use flout over flaunt.
The answer’s simple. To flout something is to express contempt for it, spit in the face of it, mock it and such; to flaunt something is to show it off, to display it ostentatiously or obtrusively (the OED’s words). So you flaunt something you like and flout something you don’t:
(1) The starlet flaunted her wealth by purchasing two diamond diadems for her puppy
(2) The starlet flouted the law by driving to the diadem store while intoxicated
What’s interesting is that this confusion suddenly sprang into existence after years of no one confusing them. Google Books returns 53 instances of someone saying “flaunt the law” between 1900 and 1940 (compared to 290 uses of “flout the law” in that time period), but not a single result for “flaunt the law” before 1900 (and 52 instances of “flout the law” before then). By a chi-square test, this has a 99% probability of indicating an increased confusion of flaunt for flout. The OED’s first attestation of flaunt to mean flout is in 1923, so apparently once the error appeared, it took off like gangbusters. That’s weird, because the similarity between flaunt and flout is phonetic. They sound the same and the former is much commoner than the latter, so people use the former when they mean the latter. Usually this sort of confusion carries a long pedigree and/or starts out slowly and only gradually becomes more common. In this case, though, it appears that no one really got confused until around 1920, and then suddenly everyone got confused. I don’t know why that would happen myself, but it’s really neat. Everyone confuses these two words now, and only 100 years ago no one seems to have. Must have been that post-WWI laissez-faire education our grandparents got.
Summary: You flaunt something you’re proud of and flout something you despise.