The term 'wavy hairstyle' can be described by two crossword solutions: PERM (4 letters) and MARCEL (6 letters). A perm is a chemical treatment used to permanently alter the structure of the hair, usually to create waves or curls. The Marcel wave is a type of permanent wave that was popular in the 1920s and 1930s. It is created by wrapping the hair around heated curling tongs and then setting it with a chemical solution. Both of these techniques are still used today to create wavy hairstyles.