Entry 1 sense Webster, 1913 Abaciscus /(ăb`ȧ*sĭs"kŭs)/ · Ab·a·cis·cus · IPA /ˌæb.əˈsɪs.kəs/ 01 n. One of the tiles or squares of a tessellated pavement; an abaculus. 1. One of the tiles or squares of a tessellated pavement; an abaculus.(Arch.)