Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
vītŭlor, āri, v. dep. n., to celebrate a festival, keep holiday, be joyful (ante-class. for exulto, gestio): is habet coronam vitulans victoriā, Enn. ap. Fest. p. 369 Müll. (Trag. v. 75 Vahl.): in venatu vitulantes, Naev. ap. Non. p. 14, 18 (Trag. Rel. p. 9 Rib.): pontifex in sacris quibusdam vitulari solet, Varr. ap. Macr. S. 3, 2; cf.: Jovi opulento, incluto … lubens vitulor, i. e. bring a thank-offering, Plaut. Pers 2, 3, 2.