n.pleochroism of a crystal so that it exhibits three different colors when viewed from three different directions
英汉双解大词典
trichroism/ˈtraɪkrəʊˌɪzəm/
1.
N（名词）
a property of biaxial crystals as a result of which they show a perceptible difference in colour when viewed along three different axes (二轴晶体)三色现象→see pleochroism