Lewis & Short

rītŭālis, e, adj. [ritus], relating to religious rites or ceremonies, ritual: rituales nominantur Etruscorum libri, in quibus praescriptum est, quo ritu condantur urbes, arae, aedes sacrentur, quā sanctitate muri, quo jure portae, quomodo tribus, curiae, centuriae distribuantur, exercitus constituantur, ordinentur ceteraque ejusmodi ad bellum ac pacem pertinentia, Fest. p. 285 fin. Müll.
Plur. as subst.: rītŭālĭa, ium, n., ceremonial rites, Amm. 17, 7, 10.
Hence, adv.: rītŭālĭter, according to religious usage, with religious ceremonies: ritualiter consecrata mensula, Amm. 29, 1, 29.