The Collaborative International Dictionary of English v.0.48:

Burggrave \Burg"grave\, n. [G. burggraf; burg fortress + graf
   count: cf. D. burggraaf, F. burgrave. See Margrave.]
   (Germany)
   Originally, one appointed to the command of a burg (fortress
   or castle); but the title afterward became hereditary, with a
   domain attached.
   [1913 Webster]