What is Impound?

Legal Definition
To shut up stray animals or distrained goods in a pound. Thomas v. Harries, 1 Man. & G. 703; Goodsell v. Dunning, 34 Conn. 257; Howard v. Bartlett, 70 Vt. 314, 40 Atl. 825. To take into the custody of the law or of a court. Thus, a court will sometimes impound a suspicious document produced at a trial.
-- Black's Law Dictionary
Legal Definition
To keep in the custody of the law; to place in a pound. See Pound.
-- Ballentine's Law Dictionary