I’ll put an attempted common sense definition out there as a straw man (fully aware of Cunningham’s law): it’s a rifle typically featuring a pistol grip and detachable magazine.
The definition needs to be intentionally vague to capture a myriad of existing designs (and the legal workarounds). I suspect there are “assault rifles” that don’t fit into this vague definition, and equally importantly: vice versa (e.g. the Barret 82A1 can’t realistically be considered an “assault rifle” by common sense).
And therein lies the problem: by being only reasonably specific, we provide too many opportunities for shenanigans (cf. Formula 1 in the 70s and 80s). But without a reasonably strict definition, we’re also creating a reasonably litigious atmosphere (“no sir, we intended this rifle for small to medium game hunting”).
Here’s another take from someone who won a Pulitzer for the times.
https://www.washingtonpost.com/style/media/2023/11/17/mona-chalabi-gaza-criticize-new-york-times-pulitzer/