That said, we can agree that it's an Indian Ocean craft and, if we exclude the modern powered types, that it has a lateen sail, right? The answer is nope on many counts.
First, let's deal with that "lateen" thing. Below, we see a true lateen sail on an Egyptian felucca.
Now let's look at the typical "triangular" sail of a dhow:
Notice how the dhow's sail is really a quadrilateral, with a short luff or leading edge, whereas the feluccas have a true triangular sail with no luff. This sail is called a settee, not a lateen. On some dhows this is very easy to mistake because the luff angles down only slightly from the line of the sail's head, but it's there nevertheless, and most easily recognized by the fact that the spar does not extend all the way to the tack or front-bottom corner.
So can we then refine the definition and say that a dhow is an Indian Ocean craft with a settee sail? No again. For starters, there have been dhows, so-called, with square sails, shown immediately below in the model of a mtepe, and below that in the confusingly-named dau la mtepe. The former, which had a sewn hull, is rather long extinct, while the latter survived into the early years of the 20th century.
Model of a mtepe (above)
A dau al mtepe (below)
But since both square-sail types are now extinct, can't we revert to the definition with the settee sail? No again, as a look at the thoni, an Indian type, shows at the top of the post. This thoni is flying an extraordinary diversity of sail types, including a settee main; a gaff spanker on the mizzen called a kose; a bome pai brailed up below it on the boom; a thanni or "water" sail hanging from the bowsprit; a settee-shaped topsail called a towser; a komitti, a rafee sail that appears just forward of the towser, flying from a stay; and a big four-sided jib called a dastoor that seems to have its upper forward corner ("throat"?) supported by a sprit or some other sort of yard. I believe there's at least one more sail flying on the mizzen but it's covered entirely by the mainsail. (The photo is a crop of the book's cover -- cropped because my scanner isn't big enough to do the whole thing. All other images from the same book.)
Bottom line, we probably can't come up with an iron-clad definition of a dhow, since it is a term that Europeans applied to just about all the sailing craft of the Indian Ocean, encompassing different rigs, hull forms, construction methods, and uses, and hailing from many different and far-flung lands and cultures. Best to think of dhows like seagulls -- there ain't no such bird as a "seagull," but it's a convenient cover-all term nonetheless and, even if you can't define it, most people know the group of birds, or boats, that you're talking about when you use it.
We'll look at dhows again in the next post.