Or"tho*dome (?), n. [Ortho- + dome.] Crystallog.
From the Note under Dome, 4:
A prism formed by planes parallel to a lateral axis which meet above in a horizontal edge, like the roof of a house; also, one of the planes of such a form.
If the plane is parallel to the longer diagonal (macrodiagonal) of the prism, it is called a macrodome; if parallel to the shorter (brachydiagonal), it is a brachydome; if parallel to the inclined diagonal in a monoclinic crystal, it is called a clinodome; if parallel to the orthodiagonal axis, an orthodome.
© Webster 1913.