Source : Webster's Revised Unabridged Dictionary (1913)

Trimorphism \Tri*mor"phism\, n. [See {Trimorphic}.]
   1. (Crystallog.) The property of crystallizing in three forms
      fundamentally distinct, as is the case with titanium
      dioxide, which crystallizes in the forms of rutile,
      octahedrite, and brookite. See {Pleomorphism}.

   2. (Biol.) The co["e]xistence among individuals of the same
      species of three distinct forms, not connected, as a rule,
      by intermediate gradations; the condition among
      individuals of the same species of having three different
      shapes or proportions of corresponding parts; --
      contrasted with {polymorphism}, and dimorphism.

   {Heterogonous trimporphism} (Bot.), that condition in which
      flowers of plants of the same species have three different
      lengths of stamens, short, medium, and long, the blossoms
      of one individual plant having short and medium stamens
      and a long style, those of another having short and long
      stamens and a style of medium length, and those of a third
      having medium and long stamens and a short style, the
      style of each blossom thus being of a length not
      represented by its stamens.