Definition of "undulation"

undulation

noun
countable and uncountable, plural undulations
1. An instance or act of undulating.
  Quotations
  But the next undulation would raise us, showing the island ablaze in the sunlight, an emerald of dazzling beauty resting lightly on the bosom of the sea.
  1929, Robert Dean Frisbee, The Book of Puka-Puka, Eland, published 2019, page 77
2. A wavy appearance or outline; waviness.
3. (music) A tremulous tone produced by a peculiar pressure of the finger on a string.
4. A wavelike curve; a smooth and regular rise and fall.
5. A wavelike motion of the air; electromagnetic radiation.
6. (medicine, dated) A feeling as if of an undulatory motion about the heart.
7. (medicine, dated) The distinctive motion of the matter within an abscess on being pressed when it is ripe for opening.