The impulsive abruptness of her movements was such that at every step the lines of her knees and the upper part of her legs were distinctly marked under her dress, and the question involuntarily rose to the mind where in the undulating, piled-up mountain of material at the back the real body of the woman, so small and slender, so naked in front, and so hidden behind and below, really came to an end.
There are no more uses of "undulate" in the book.
Show samples from other sources
A sidewinding snake uses less energy to cover the same distance as a laterally undulating snake uses.
The dancers’ arms undulated in unison to add to the ethereal effect.