"Says You" had one answer:
Naturalize - the process of putting an object into its natural state. The contradiction lies within the notion that an object can artificially be put into a natural state. As Wes commented, this is a euphemism, and isn't used literally.
And my answer:
Nondescript - "lacking distinctive qualities" or "not easily described". Hm, if only there were an adjective that could easily describe that distinctive quality of an object. Hey, there is, it's "nondescript". Similarly, using 'indescribable' to modify a noun is an act of description. Oops.
This one isn't a euphemism, I just think of it as a weird construction.