Lookups on Merriam-Webster spiked on September 8, 2010.
On September 7, The Baltimore Sun ran the headline, "Opposing votes limn difference in race."
That unusual word choice ended up making headlines of its own.
One reader described the usage as "unbelievably arrogant and patronizing." Others thanked the paper for expanding their vocabularies.
Responding to the controversy, the paper's eminent blogger about language, John McIntyre, pointed out that it "may not have been the shrewdest choice for the front page." However, he added, "Speaking as a language maven, I applaud when people consult dictionaries to add another little brick to the wall of their vocabularies. Now that you know what it means, it is yours forever."
Limn means "to outline in sharp detail" or "to describe." It's a close relative of illuminate.