Wavy lines are a type of line that is characterized by its undulating shape. The term 'wavy lines' can be represented by two different crossword solutions: 'wiggles' (7 letters) and 'esses' (5 letters). Wiggles are a series of short, curved lines that are connected together, while esses are a series of S-shaped curves. Both terms are used to describe the same type of line, but they have slightly different meanings.