I always thought that simulacrum was a word invented by someone like Stanisław Lem, who was very fond of coining words.
But it turns out that the word really does exist.
I learned this from the Word Of The Day RSS Feed from dictionary.com via Google Web Clips in Gmail.
simulacrum \sim-yuh-LAY-kruhm; -LAK-ruhm\, noun;
plural simulacra \sim-yuh-LAY-kruh; -LAK-ruh\:
1. An image; a representation.
2. An insubstantial, superficial, or vague likeness or semblance.
Discovery
2006-03-04