We don't have synonyms for drock yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are rock, dock and frock.
(n) :
(UK, dialect) A drainage ditch, sometimes covered; a small watercourse, especially one used for drainage or sewerage.
(n) :
(possibly obsolete) A part of certain 18th and 19th century models of plough: a piece of wood which forms the bottom part of the plough, to which the spindle and the shelve-boards are fastened.
(n) :
(UK, dialect) A drainage ditch, sometimes covered; a small watercourse, especially one used for drainage or sewerage.
(n) :
(possibly obsolete) A part of certain 18th and 19th century models of plough: a piece of wood which forms the bottom part of the plough, to which the spindle and the shelve-boards are fastened.