merohedraladj.
/ˌmɛrə(ʊ)ˈhiːdr(ə)l/, U.S. /ˌmɛroʊˈhidr(ə)l/ Crystallography.
Of a crystal or crystal form: having one half, a quarter, or one eighth of the maximum number of faces possible for its crystal class; merosymmetric. Cf. holohedral adj.
ΚΠ
1871 N. Story-Maskelyne in Philos. Trans. (Royal Soc.) 161 360 This investigation was made exceptionally difficult by the very partially developed or merohedral character of the crystals.
1878 Nature 26 Dec. 171/1 In his discussion of merohedrism the author [sc. H. P. Gurney, who uses only the synonymous word ‘merosymmetric’] has not attended to the limiting condition..that the merohedral form should not be identical with the characteristic form of a system of lower symmetry.
1895 N. Story-Maskelyne Crystallogr. §137 The term merohedral will be reserved for certain cases in which a defalcation is met with in the faces of a crystal out of accord with any fixed law of symmetry; though sometimes such a merohedral crystal simulates the mode of grouping of a crystal belonging to a different type of symmetry from its own.
1938 Amer. Mineralogist 23 178 For this purpose the terms holohedral and merohedral have usually been used.
1992 European Jrnl. Mineral. 4 1218/1 We interpret these domains as being merohedral twins.
This entry has been updated (OED Third Edition, September 2001; most recently modified version published online March 2022).
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adj.1871