Depersonification is (yeah, you guessed it!) the opposite of personification : giving a human the qualities of an inanimate or non living object. Be careful with this one, though, because you don't want to get it mixed up with a Metaphor. Though the two are closely related, they do have differences. See the examples below.
the man's stony hands caused him to drop the plate he was holding.
note, that if you were to say "the man's hands were stone,", you would be using a metaphor. The statement above more closely exhibits depersonification, in that it uses the object (stone) as an adjective for the man's hands, rather than a noun.