Imbrute, v. t. [imp. & p. p. Imbruted; p. pr. & vb. n. Imbruting.] — Webster enters it under “imbrute”
Etymology: [Pref. im- in + brute: cf. F. abrutir. Cf. Embrute.]
To degrade to the state of a brute; to make brutal. And mixed with bestial slime, This essence to incarnate and imbrute. Milton.
1 other Webster entry under this spelling
Imbrute, v. i.
To sink to the state of a brute. The soul grows clotted by contagion, Imbodies, and imbrutes, till she quite lose The divine property of her first being. Milton.
Shades of meaning
Fernald has no entry of its own for imbruted; he lists it under brutish.
He lists it without comment; the entries above explain its neighbors.