What type of solid lacks a definite and orderly structure?

The correct choice refers to amorphous solids, which are characterized by their lack of a long-range, ordered arrangement of particles. Unlike crystalline solids, which have a well-defined geometric structure and repeating patterns, amorphous solids do not exhibit any systematic arrangement. This absence of order results in different physical properties compared to their crystalline counterparts.

Amorphous solids can be seen in materials such as glass and certain types of polymers. Their irregular structure contributes to their unique properties, such as isotropy, meaning their physical properties are the same in all directions, unlike crystalline solids which can display anisotropy due to their directional order.

In contrast, cubic, crystalline, and metallic solids all possess a certain degree of internal order and regularity in their atomic arrangements, making them distinct from amorphous solids.