The second-largest teachers union in the country committed an embarrassing language mistake in an early 2016 presidential primary ad airing in New Hampshire.

"I love when I teach something and they get it...and they literally light up," a teacher says in the American Federation of Teachers commercial. It was unclear what subject or grade the teacher is supposed to be teaching.

It's also unclear whether the teacher is using the new, second meaning of the word, which makes "literally" a synonym for "virtually" or "figuratively," or the traditional — or literal — definition of the word. If it's the latter, then I have to ask: When the teacher's students learn something new, do they light up a cigarette? Do they start glowing as if a lightbulb inside them has just starting shining? Either would be cause for concern.

It seems likely that AFT meant "literally" in the slang sense of the term. If so, it would be taking a bold stance in favor of the new meaning. So many people find that use of the word annoying that Time Magazine included it on its list of words that should be banned in 2015.

It remains to be seen how many English teachers, if any, will literally decide to give up their union membership over this issue. If we can't trust the AFT to use the correct definition of "literally," how can we trust it to shape our nation's education policy?

Merriam-Webster added the informal definition of "literally" to its pages in 2013.

The American Federation of Teachers represents 1.6 million members across the country.

(Hat tip to Alexander Russo at Washington Monthly for catching the mistake.)