Definition: to treat (someone) in a very harsh and usually violent way
The most common sense in which one typically encounters brutalize today is the one which refers to treating a person or thing in a brutal manner. However, the original meaning of the word in English was “to make brutal, unfeeling, or inhuman.” The earliest use of brute in English came in the 15th century, as an adjective, with the meaning “of, relating to, or typical of animals, brutes, or beasts; not possessed of human rational powers.”
As to the conjugal pleasure, and the sport of Venus, the effects thereof are so direful and hurtful, that I wonder men will be such slaves to it; for it doth not onely invalidate and infeeble the vigour of the spirit, but render the mind base and cowardly, dull the vivacity of the understanding, brutalize the judgment, waste the memory, occasion repentance, as saith Aristotle, and as Demosthenes also in this case answered.
—Oliver Jacques, A Discourse of Women, Shewing Their Imperfections Alphabetically, 1662