has been undulating

• present perfect progressive

  present perfect progressive

  Used to describe an action that began in the past, has continued continuously, and is still in progress.

  of undulate (3rd person singular).
  undulate

  verb (used without object)

  to move with a sinuous or wavelike motion; display a smooth rising-and-falling or side-to-side alternation of movement.

Related Words

• billow
• wobble