According to the new definition, if it looks scary then it's probably an "assault rifle". 

Via The Federalist: 

Soon after the school shooting in Parkland, Florida, Merriam-Webster’s online dictionary changed its definition of “assault rifle.”

The entry for “assault rifle,” which was updated March 31, 2018, reads as follows:

noun: any of various intermediate-range, magazine-fed military rifles (such as the AK-47) that can be set for automatic or semiautomatic fire; also : a rifle that resembles a military assault rifle but is designed to allow only semiautomatic fire

After 17 people were shot and killed at Marjory Stoneman Douglas High School in February, activists have been using the tragic events to make the sale of so-called “assault weapons” illegal.

An Internet archive search shows the Merriam-Webster entry for “assault rifle” appears to be different now than it was before the shooting. A cached version of the same entry from June 13, 2016 has this definition:

noun:  any of various automatic or semiautomatic rifles with large capacity magazines designed for military use

“Assault weapon” and “assault rifles” are malleable terms often used in public discourse to scare people. After all, all guns are designed to “assault” something. The usual proper use of this term is to describe fully automatic machine-gun-style weapons, which in the United States have been banned from civilian use for years. Notice that the Merriam-Webster change stretches this definition to include anything that looks like such a gun regardless of whether it shoots like one.

Read more here.