The Collaborative International Dictionary of English v.0.48:

Dirk \Dirk\, a. [See Dark, a.]
   Dark. [Obs.] --Chaucer.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dirk \Dirk\, v. t.
   To darken. [Obs.] --Spenser.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dirk \Dirk\, n. [Ir. duirc.]
   A kind of dagger or poniard; -- formerly much used by the
   Scottish Highlander.
   [1913 Webster]

   Dirk knife, a clasp knife having a large, dirklike blade.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dirk \Dirk\, v. t. [imp. & p. p. Dirked; p. pr. & vb. n.
   Dirking.]
   To stab with a dirk. --Sir W. Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dirk
    n 1: a relatively long dagger with a straight blade