reverse engineering is usually about trying to understand a partially/mostly concealed system/interface, while for this case everything is already visible, but hard to understand.
By that definition, analyzing compiled native code would be "un-obfuscating".
IMO, deobfuscation is a subset of reverse engineering - which at a push I would define as "taking a program from the form it is distributed into a preferred form for modification/understanding".
IMO, deobfuscation is a subset of reverse engineering - which at a push I would define as "taking a program from the form it is distributed into a preferred form for modification/understanding".