/un'jeuh lay"sheuhn, un'dyeuh-, -deuh-/ , n.
1. an act of undulating; a wavelike motion.
2. a wavy form or outline.
3. one of a series of wavelike bends, curves, or elevations.
4. Physics.
a. a wave.
b. the motion of waves.
[ 1640-50; UNDUL(ATE) + -ATION ]