Reticulation is a term used to describe a pattern or network of lines, often seen in nature. It is also used to refer to the process of creating such a pattern. The term is derived from the Latin word 'reticulum', meaning 'NET'. In a crossword puzzle, the term 'MESH' is often used as a synonym for reticulation. MESH is a four-letter word that can be used to describe the same pattern or network of lines.