Answer: An Implied shape
Step-by-step explanation:
An implied shape is not a traditionally defined shape. The at&t logo, although resembling a sphere does not have a continuous border. It instead uses lines to infer a spherical shape.
The designer, Saul Bass uses a viewer's existing knowledge of what a sphere looks like, gets the viewer to see the logo as a sphere.
This kind of implied shape can also be seen in Sauerkids pieces. In their works, lines are not continuous but shapes are clearly implied.