What is Blanket Policy?

Legal Definition
Blanket policy is a policy which behaves similarly to a variety of things. Based on Webster's Dictionary it "covers a group or class of things or properties instead of one or more things mentioned individually, as where a mortgage secures various debts as a group, or subjects a group or class of different pieces of property to one general lien."
-- Wikipedia
Legal Definition
A policy of fire insurance which contemplates that the risk is shifting, fluctuating, or varying, and is applied to a class of property rather than to any particular article or thing. Insurance Co., v. Baltimore Warehouse Co.., 93 U. S. 541, 23 L. EM. 868.
-- Black's Law Dictionary
Legal Definition
An insurance policy covering generally the interest of the insured without describing particular property. See 23 L. Ed. (U. S.) 869.
-- Ballentine's Law Dictionary