For me solid means a long boring game whose eventual outcome is of far less interest than the relief felt that the game is finally over. But then we all have our specialities and that's mine...
OK to be a little more serious. It depends. On everything. The players, the opening, the variation, the goal of the players ( a super GM needing a win is going to play a solid opening differently from when he just needs a draw), and of course the pawn structure chosen. You ask a good question, but book chapters have probably been written in an attempt to answer it.
Im understanding that solid is kind of the opposite of sharp/tactical. But is solid and drawish kind of the same thing? Do solid players still have 100% intentions to win instead of draw? Does solid mean strategically rich? Or unpenetrable?