In the prologue I hear a good many enemy soldiers shout this refrain as they charge at me. I presume when they say 'plough' they don't mean it in the agrarian sense, but I think I'm missing some cultural context here because I don't quite understand how Geralt is 'the lily'.
What exactly do my enemies mean when they scream 'plough the lily'?
1 Answer
Lily refers to Temeria in this case. At the beginning of the Witcher 2 you're fighting for Temeria. The emblem for Temeria are silver lilies on black background:
Ploughing does refer to what you're suspecting, "plough the lily" means pretty much "fuck Temeria".
The Witcher Wiki also explains this particular phrase in the trivia section:
3The term "Lilies" is used as a collective noun, likely meant to be derogatory, referring to the people from Temeria. A common phrase used by non-Temerian NPC enemies in The Witcher 2 is, "Plough the lilies!" The term most likely originates from the silver lilies in Temeria's emblem.