Emily Dickinson Lexicon

MOR'TAR, n.² [D. mortel; Fr. mortier; G. mörtel; Sp. mortero; It. moirteal. In other languages, as in English, the orthography of this word and of the last is the same, and perhaps this name is taken from beating and mixing.]

A mixture of lime and sand with water, used as a cement for uniting stones and bricks in walls. If the lime is slaked and the materials mixed with lime-water, the cement will be much stronger. Encyc.