I've seen some references to the term "MLD" but have failed to find a definition in any list of MTG terminology or slang. What does this mean?
Or, to quote one of the moderators on MTGSalvation:
MLD is mass land destruction, so generally speaking, any card that destroys multiple lands at once. This is usually indiscriminate, so Ruination is considered MLD while Sylvan Primordial is not. Back to Basics, and things that prevent you from using lands are not MLD, simply resource denial. At least, that's my take. I don't think the term has made its way into Webster's yet.
So you're right, it's not an official Magic: The Gathering term.