Webster's Dictionary 
(n.) A stone.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
(the stone), a surname of Jupiter at Rome, as is evident from the expression "Jovem Lapidem" (Cicero, ad Fam. 7:12; Gellius, 1:21; Polybius, 3:26). It was formerly believed that Jupiter Lapis was a stone statue of the god, or originally a rude stone serving as a symbol, around which people assembled for the purpose of worshipping Jupiter. But it is now generally acknowledged that the pebble or flint-stone was regarded as a symbol of lightning, and that therefore, in some representations of Jupiter, he held a stone in his hand instead of the thunderbolt (Arnobius, adv. Gent. 4:25). Such a stone (" lapis Capitolinus," August. De Civ. Dei. 2:29) was even set up as a symbolic representation of the god himself (Serv. ad AEn. 8:641). When a treaty was to be concluded, the sacred symbols of Jupiter were taken from his temple, viz. his scepter, the pebble and grass from the district of the temple, for the purpose of swearing by them ("per Jovem Lapidem jurare," Livy, 1:24; 30:43). A pebble or flint-stone was also used by the Romans in killing the animal when an oath was to be accompanied by a sacrifice, and this custom was probably a remnant of very early times, when metal instruments were not yet used for such purposes. — Smith, Dict. Greek and Romans Biog. and Mythol. s.v.