Wiley is a publisher. I don’t think there is such as a thing as “Wiley dictionary”
“Just type in Multiple Shooting, leave out the word Define!”
Did that too.
I get when I type in “multiple shooting” I get several hits to mass shootings including the congressional baseball game, a mass shooting in Chelsea in may. An Orlando workplace shooting in Orlando in june. A mass shooting in a nightclub in little rock. Etc etc all these are labeled mass?shootingvand or multiple shooting often in the same article.
See for example this article “Multiple shooting, police chase leave at least 3 dead” about a shooting in Savannah on July.
The article begins “The Savannah-Chatham Metropolitan Police Department is investigating after a mass shooting …”
There does not seem to be a real or practical difference between the two