The Collaborative International Dictionary of English v.0.48:

Dogtooth \Dog"tooth`\, n.; pl. Dogteeth.
   1. See Canine tooth, under Canine.
      [1913 Webster]

   2. (Arch.) An ornament common in Gothic architecture,
      consisting of pointed projections resembling teeth; --
      also called tooth ornament.
      [1913 Webster]

   Dogtooth spar (Min.), a variety of calcite, in acute
      crystals, resembling the tooth of a dog. See Calcite.

   Dogtooth violet (Bot.), a small, bulbous herb of the Lily
      family (genus Erythronium). It has two shining flat
      leaves and commonly one large flower. [Written also
      dog's-tooth violet.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

dogtooth
    n 1: perennial woodland spring-flowering plant; widely
         cultivated [syn: dogtooth violet, dogtooth,
         dog's-tooth violet]
    2: one of the four pointed conical teeth (two in each jaw)
       located between the incisors and the premolars [syn:
       canine, canine tooth, eyetooth, eye tooth,
       dogtooth, cuspid]
    3: a carved pyramidal ornament; used in 13th century England