The state of an online forum thread which has been locked by an administratior or moderator on the basis that the subject matter is too trivial to warrant further discussion. Typically a concluding post is made by the moderator to the effect that the discussion to date has made a "mountain out of a molehill" before the thread is locked for further discussion. Threads tending towards criticism of the moderator's organisation may sometimes be pre-emptively molehilled to avoid further negativity to propagate.
Poster1: Hey, respond to my post about Germaine Greer's new book!
Poster2: I can't. It's been molehilled.
Moderator: This is going nowhere. Molehilled.