The Collaborative International Dictionary of English v.0.48:

Mirk \Mirk\, a. [See Murky.]
   Dark; gloomy; murky. --Spenser. Mrs. Browning.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mirk \Mirk\, n.
   Darkness; gloom; murk. "In mirk and mire." --Longfellow.
   [1913 Webster]