If a circle with another circle cut out is called a washer, what's the spherical equivalent called? A circle with a smaller concentric circle cut out of it is called a washer. What would a sphere with a smaller concentric sphere carved out of it be called?
An example is the shape of the first structure in the image below:

By Mariana Ruiz Villarreal ,LadyofHats - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3032610
 A: As the comment says, the term is spherical shell:

In geometry, a spherical shell is a generalization of an annulus to three dimensions. It is the region of a ball between two concentric spheres of differing radii.

A: Short Answer: The object described in the question is a spherical shell.
Further Discussion:

*

*A disk with a smaller disk removed is an annulus.
A washer is a small, flat, usually circular (though other shapes exist) piece of metal with a hole in the middle of it.  Washers are a real-world device typically used for spacing—as such, one of the essential properties of a washer is that it has thickness.  In elementary calculus classes, students are often taught to find the volume of a solid of rotation using the "washer method".  This method approximates the volume of the solid using washer-shaped solids, which are probably better described mathematically as cylinders with annular bases.
In general, I would probably avoid using the term "washer" in any mathematical context beyond an elementary calculus class.  As demonstrated by the original question, the term does not seem to have a clear meaning (the asker uses "washer" as a synonym of "annulus"; I think that many others would understand a washer to be a short cylinder with an annular base).  If one insists on using the term, a sentence or two explaining what, precisely, is meant would be helpful.


*In higher dimensions (more general metric spaces), the analog of an annulus is a spherical shell, which is the solid region between two concentric spheres of different radius.  Alternatively, a sphereical shell is a ball with a smaller ball (with the same center) removed.
In a metric space $(X,d)$, a ball is the collection of all of the points within a fixed radius of a specified point (the center).  The open ball $B(x,r)$ with radius $r$ and center $x$ is the set
$$B(x,r) = \{ y \in X \mid d(x,y) < r \}, $$
and the closed ball $\overline{B}(x,r)$ with radius $r$ and center $x$ is the topological closure of the open ball with the same center and radius.  Given two radii $r_1$ and $r_2$ with $r_1 < r_2$, and a fixed point $x$, the spherical shell with inner radius $r_1$, outer radius $r_2$, and center $x$ is the set
$$ \overline{B}(x,r_2) \setminus B(x,r_2). $$
In $\mathbb{R}^3$ (three dimensional Euclidean space), this becomes
$$ \left\{ y \in \mathbb{R}^3 \mid r_1 \le \|x - y\| \le r_2 \right\}, $$
which is precisely the shape described in the question, above.  If $\mathbb{R}^3$ is replaced with $\mathbb{R}^2$, then the definition reduces to the definition of an annulus.
