I. ˈ ̷ ̷ ̷ ̷ˌlād.ə(r), -ātə- noun
( -s )
: one that undulates
a lovely blonde lady undulator — Wall Street Journal
II. noun
: a device consisting of a series of magnetic dipoles of alternating polarity into which a stream of particles (as electrons) moving at relativistic velocity is injected to produce intense essentially monochromatic coherent synchrotron radiation at a very few wavelengths