Materialism means "material precedes idea" and dialectic means contradiction/struggle between opposing forces. All that exists is in continuous momentum and constant change due to contradiction/struggle with forces, like electron and proton in an atom, earth and sun tied and moving in gravitational tension.
How a seed, as a consequence of internal contradictions/unity of opposites, evolves into a tree and flowers. How with external contradiction and force of labour changes cotton into a piece of clothing that takes the function and form of a dress. Therefore Dialectical Materialism basically means "material in constant change as a result of contradictions". It is not a form of logic, it is not a tool to predict the future, it is rather a mode of thinking. It is the conception of change in the material within its inner contradictions and its relations with other systems as a relation and a process simultaneously in the form and function, within the framework of existing social reality.