1. n. [Drilling]

In general, a funnel-shaped device used to transfer products. The hopper is often at the bottom of any container for holding or using bulk products, especially drilling fluid additives and cementing material.

2. n. [Drilling]

The device used to facilitate the addition of drilling fluid additives to the whole mud system. While several types of hoppers exist, they generally have a high velocity stream of mud going through them and a means of mixing either dry or liquid mud additives into the whole mud stream. The resultant mixed mud is then circulated back into the surface mud system. A hopper is generally used to introduce relatively small quantities of additives to the mud system.