I spent two years in an occupation where the most entertaining thing to do was to read the dictionary for fun. The fact that someone, somewhere, defined a difference between the hyphenated and compound forms of the term doesn't mean that everyone is using those forms as defined; thus my request for disambiguation remains relevant.

Edit: also:

    $ dict groundbreaking
    2 definitions found
    
    From The Collaborative International Dictionary of English v.0.48 [gcide]:
    
      groundbreaking \ground"break`ing\ n.
         The ceremonial breaking of the ground to formally begin a
         construction project. It is sometimes carried out by an
         official who digs the first spadeful of dirt from the ground,
         to begin the preparatory excavation work.
      
         Syn: groundbreaking ceremony.
              [WordNet 1.5] groundcover
    
    From WordNet (r) 3.0 (2006) [wn]:
    
      groundbreaking
          adj 1: being or producing something like nothing done or
                 experienced or created before; "stylistically innovative
                 works"; "innovative members of the artistic community";
                 "a mind so innovational, so original" [syn: {innovative},
                 {innovational}, {groundbreaking}]
          n 1: the ceremonial breaking of the ground to formally begin a
               construction project [syn: {groundbreaking},
               {groundbreaking ceremony}]