Something that is structureless lacks a specific form, whether it's free-flowing music, a workplace with no rules or bosses, or a big glop of warm mayonnaise. In physics, something structureless cannot be broken down into smaller parts.
Many physicists consider an electron (like other parts of an atom) a structureless particle: it has only one known part — itself! More often, though, we say something is structureless if it's not firm or fully solid. Some people might refer to jello as being structureless. In music, art, and poetry, structureless works do not follow a particular form or pattern. And organizations that are structureless may not have designated leaders, job descriptions, or regulations — like a classroom with no teacher or rules.