WHO has some very specific guidelines about how it classifies an infectious disease outbreak. A novel infection that demonstrates sustained human-to-human transmission in more than one region is their basic definition. Note that severity or lethality is not part of the definition, which turned out to be somewhat of a liability in the case of H1N1 since so far, it produces mild symptoms in most people it infects, and many people thought a Level 6 designation was crying wolf. The avian flu was novel to humans and highly lethal, but it never managed sustained human-to-human transmission, so it never got that far in the WHO scale.

There isn't really another alternative to the term "pandemic". Don't forget the term "endemic". Arguably, HIV could be endemic because it is well entrenched in many parts of the world, like malaria is. Only when the frequency of disease is higher than expected do we classify a disease as an "epidemic" or "pandemic".

I think that the WHO pandemic scale, like many other tools/guidelines used by planners, gets misused/misinterpreted when absorbed by the general public. Terms that have specific meanings to help make decisions could have very different meanings to the general public, like the word "pandemic". The average person may assume that any "pandemic" must be lethal, but from a public health planning/execution standpoint, that's not necessarily true.