I heard this on the radio yesterday and saw it on Wikipedia also, the title sounds good, but at least we know it now

Harry Potter and the Deathly Hallows

 

The definition of hallow is:

Hallow: To make scared||To revere as holy

 

So, it (Probably)could be one of three things--

A) It is a very scary. . . well, death machine. I don't think that'd fit. Unless Voldemort has another "weapon."

Objects that when you think it's holy you die. Nuh-uh.

C) Most likely, J.K. is reffering to the Horcruxes. Deathly, as in if they are destroyed, Voldemort will be as well. Hallow, as in they inflict fear, and make you give up hope. What are the chances you're going to be able to destroy 7 parts of a soul?

 

I underlined C because it was the most likely. . . A and B, just don't think so.

The definitions that you found are for when hallow is a verb -- i.e. to hallow a sacred spot.

But hallow in the title is a noun. A pluralized one at that.

As a noun, "the hallows" are more of just a sacred area of sorts.

Oh, and it's sacred, not scared.

-KIE