D defs.my
Entry 1 sense Webster, 1913

Orthoclase

/ôr'-thək-lāsˌ/ · Or·tho·clase · IPA /ˈɔrθəklˌeɪs/
01 n. Common or potash feldspar crystallizing in the monoclinic system and having two cleavages at right angles to each other. See Feldspar.
  1. 1.
    Common or potash feldspar crystallizing in the monoclinic system and having two cleavages at right angles to each other. See Feldspar.(Min.) See: Feldspar