To directly answer the question: “High Mobility Multipurpose Wheeled Vehicle” [0]

[0] https://en.m.wikipedia.org/wiki/Humvee

It's the military term for Humvee - the huge vehicle that was popular for a while when gas was cheap. Or rather "hum vee" is how it is pronounced and the civilians spelled it phonetically.

"Hummer" was the brand name of the consumer version:

https://youtu.be/GEMRkQmh9WI

I originally wrote hummer, but I thought that was a slang term. Thanks