In short, in his bringing up he has been so nursed by Law and Equity that he has become a kind of fossil imp, to account for whose terrestrial existence it is reported at the public offices that his father was John Doe and his mother the only female member of the Roe family, also that his first long-clothes were made from a blue bag.
There are no more uses of "terrestrial" in the book.
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Unless we’ve launched some kind of classified aircraft, no way this thing is terrestrial."
Rick Yancey -- The 5th Wave
My own pessimism, my insecurity, was a more terrestrial affair.