ululate \UL-yuh-layt; YOOL-\ (intransitive verb) - To howl, as a dog or a wolf; to wail; as, ululating jackals.
"The other women thronged to her. They began to ululate again, rolling their tongues so that their spittle flew as they emitted that terrible keening sound." -- Wilbur Smith, 'The Triumph of the Sun'
Ululate derives from Latin ululare, to howl, to yell, ultimately of imitative origin. The noun form is ululation; the adjective form is ululant.