A more thorough explanation:

Definition: An engrosser is a person who has the responsibility of writing or copying legal documents. In the past, an engrosser was also someone who bought a lot of a certain product to try and control its price.

Example 1: The lawyer hired an engrosser to write up the legal contract.

Example 2: In the 1800s, some people became engrossers of wheat, buying up large amounts of it to try and control the price.

These examples show how an engrosser can be someone who writes legal documents or someone who tries to control the price of a product. The first example shows an engrosser in the modern sense, where they are hired to write up legal documents. The second example shows an engrosser in the historical sense, where they would buy up a lot of a product to try and control its price.