Anyone that believes Joseph Smith was a prophet and the Book of Mormon is scripture can call themselves Mormon. Anyone putting restrictions on the word doesn’t have the right to get upset when someone says Mormons aren’t Christian.
Anyone can write a dictionary though, Eric. What makes a dictionary definition authoritative, particularly for deeply context-embedded words like “Mormon” and “Christian”? The dictionary definition is likely to gloss over most nuances.
Furthermore, just as with “Christian,” it’s not unreasonable for words to have multiple, overlapping definitions. Actually, it happens all the time. Welcome to linguistics. When I personally talk about “Mormons,” I’m usually just referring to the mainstream LDS church. But Someone else could reasonably use the term in another context to include the RLDS, FLDS, Strnagites, and Rigdonites. There’s not some rule laid down by the gods of linguistics that says words can only have one “correct” meaning. And nobody authoritatively owns words, really. I mean they can claim to own words, and other people might even respect that claim, but practically speaking it’s preposterous.
Words are given definitions by their usage. It might actually be a better poll to ask people what definitions for “Mormon” they use, and allow for multiple selections.