halberd of defense (80s) is a special item. eternium halberd of defense just has defense ego (+4 DV in defensive or something).

wouldn't it be better to change the 80s halberd of defense to 'of repelling' or 'of deflection' to avoid confusing cases like this? [even more when you get an iron halberd of defense [100s] and another one [80s]]

It's clearly a problem, but I think it is fine as-is. As I noted in IRC:
20:23:17 < sirtheta> you would think with all the emphasis on item weight in adom, people would readily notice the difference between 80s halberd of defense and suffixed halberd of defense
20:23:26 < sirtheta> but i've now seen two bug reports that confuse the two, odd

If you can't tell the difference based on the weights, well, that's that :)

It is clearly a matter of confusion. The special item "halberd of defence" should be changed to "halberd of parrying" to match the similarly named sword.

I'd rather it be something specific to the halberd, rather than just mimicking a different weapon's name. Something like, say, "halberd of anticipation", or "halberd of the pivot", or "halberd of rebuff".

I actually rather like Grey's suggestion. It does clearly delineate and provides some consistency.

I kind of like 'of defense'. It gets straight to the point. Tells you exactly what it does.

I like the current name, personally.