The Collaborative International Dictionary of English v.0.48:

Undulate \Un"du*late\, v. t. [imp. & p. p. Undulated; p. pr. &
   vb. n. Undulating.]
   To cause to move backward and forward, or up and down, in
   undulations or waves; to cause to vibrate.
   [1913 Webster]

         Breath vocalized, that is, vibrated and undulated.
                                                  --Holder.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Undulating \Un"du*la`ting\, a.
   Rising and falling like waves; resembling wave form or
   motion; undulatory; rolling; wavy; as, an undulating medium;
   undulating ground. -- Un"du*la`ting*ly. adv.
   [1913 Webster]