Here are just a few definitions that are commonly misunderstood, or not understood at all.
Massive: in gemological terms, massive means a mineral that is present without any crystal structure; for example, see these two photos:
You see the one on the left have a regular crystal growth; the one on the right has no crystalline structure, therefore it is massive.
Oxidizing: Any oxidized substance is a substance that has grabbed on to, or attached with, Oxygen. Rust is oxidized Iron, tarnished Silver is just silver that has grabbed onto oxygen, and is covered with a small layer of it.
Weld: This means to fuse, or melt together, any to metals for a specific purpose. The most common technique for welding steel is with a torch, where a torch is applied to the joint where the two steels are to be welded, and they are melted together, sometimes with the help of a separate steel rod to fill in the holes and void. Heating up the two steels and pounding them together with a hammer is also a way to weld, as the force and heat fuse the two surfaces into each other.