Pretty much any utilitarian/commercial use wall mounted light like in the pic above. Usually has more light output than your typical residential wall mounted light and uses a HID or LED light source.
I believe the original Wallpacks were the old
Holophane ones that had the ballast mounted externally above the fixture. The name has gotten genericised over the years to refer to any manufacturer's fixture with a similar form factor.
The closely related term,
tallpack is I believe originally a RAB trademark but is often used to refer to those compact wallpacks that are taller than they are wide. Usually either low watt HPS/MH or LED. And in the case of the HID models, use a smaller medium based lamp.