Okay, I think this one should be fairly straightforward, but it's come up twice in my recent reading, and I realize that I am not quite comfortable with my understanding. I think it means something like to be separated from one's race or culture, or homogenized into some raceless state. Now it's time to search for the definition.
Well, it's close, but as I suspected, not quite right. What it really means is to be uprooted, or pulled out by the roots. The base of the word is a French word for root, not race, although I suppose they could be related. The second definition, to be displaced from one's native custom or environment, is closer to my thought, but all that means is that when I'm reading the word in a sentence, I've been able to puzzle out an approximate meaning that usually fits.
It's not always an innocent word. It can also mean to eradicate or to cut off from existence.
Deracination. Think carrots being pulled and the concept will stay with you.