Making the rounds lately is the prospect that Merriam-Webster has “changed” the entry for “assault rifle” in context with the Parkland shooting, or in response to a politically-motivated push to alter how we use words. However, this possibly very misleading.
Merriam-Webster does appear to have augmented the entry for “assault rifle” but the problem lies mostly in the understanding of what a dictionary entry is designed for.
A dictionary describes usage. Think of a newspaper sports page that lists which teams scored how many points in recent games — are those reports “defining” (or prescribing) how many points those teams are allowed to score? No, they are just observing the outcome of those games, and reflecting that data on the page.
Likewise, a dictionary is not prescribing meaning, or designating official meaning of words — it is describing statistics about how words are observed to be used. A dictionary also does not comment on the truthfulness that usage; a dictionary simply observes how the general public uses words, and then ranks the way they use words starting with the most-commonly observed way. That’s the whole reason they’re even listed in order of 1-2-3 to begin with. The first meaning isn’t more correct, it’s simply more popularly used that way.
This same controversy arose in ~2008 when M-W and others like it updated the entry for marriage to include usage to refer to unions other than strictly male-female pairs, and it was then also argued that the dictionary was bowing to political pressure, or trying to “change the definition of marriage” as if it announced mandates for official correctness — but it doesn’t do that to begin with. It observes how the general public uses words, and reflects that usage, statistically. The idea that “the dictionary” provides official meanings, or correctness/incorrectness of meanings, simply isn’t true.
Your favorite word board game may use “a dictionary” to officiate which words are playable in the context of the game, but this ain’t Scrabble, honey.
If you’re interested to learn more about the concepts of descriptive and prescriptive linguistics (or about how dictionaries aren’t the officiators of English), consider reading, “All English Grammar Questions Answered At Once: Is it this way, or that way?” for a few citations and expansion on concepts mentioned above.