Kathryn Catania of Northwest Washington looked up at a Metrobus sign at Seventh Street and Constitution Avenue NW outside the National Gallery of Art and didn’t get it.

She wrote to us saying she was “dumbfounded” by the phrasing and thought other riders might be as well.

In an e-mail, Catania, who calls herself a Metro rider and advocate for plain language, wrote, “I thought to myself what does alight mean?”

She said she recalled using it in a college poetry class, “usually in connection with birds landing on something.”

Using her phone, she said she found it on Merriam-Webster’s online dictionary.

The meaning: intransitive verb. 1. to come down from something (as a vehicle); as a: dismount. b. deplane. 2. to descend from or as if from the air and come to rest. 3. archaic: to come by chance.

Catania said she assumes Metro is using the first definition, although she notes “we all know sometimes Metrobus does come by chance instead of by schedule.”

Catania wondered “why they didn’t say ‘Exit Only for X, Y, Z routes’ ” instead of “Alight Only.”

“Bus riders shouldn’t have to look up the language on the bus sign to decipher what it says,” she wrote.

The sign at Seventh and Constitution seems to imply Alight Only, or exit only, for routes P17, P19 and W13.

Dan Stessel, Metro’s chief spokesman, said the sign means passengers can “discharge” for these routes at the stop but the bus won’t “accept new passengers” for those routes at the stop.

As to why the second part of the sign reads, “16F, 32, 36, 54, 74 Only,” he said at first that it was “clearly a mistake.”

But he wrote in a later e-mail, “upon further research, it appears that the sign it replaced contained the word only as well.” Bus officials, he said, believe “it is because there are so many routes that pass the location without stopping — so the word ‘only’ was added at some point to reduce confusion.”

The sign is part of Metro’s “new sign standard,” according to Stessel.

They new signs are bigger and comply with the Americans with Disabilities Act, with larger font size. Metro has put in 500 of the new signs and it will take three years to install new ones at Metro’s 11,000 bus stops around the region under a $2.5 million plan to put in new poles, Braille and lettering.

How many use the word alight?

Stessel wrote, “we don’t have a count on this.”

And why use the word alight on bus signs?

Stessel said it is “a word and a fairly common one at that.”

He wrote in an e-mail response, “The current sign system is the result of a regional collaboration with bus stop coordinators throughout the region. The other operators in the region also use the term ‘alighting.’

“It is not just a colloquial phrase of Metro.”

Catania spotted another bus stop sign that used the word alight at Massachusetts Avenue and First Street, across from the National Postal Museum. It reads “97, D8, X8 Layover Alighting Only.”

She advocated for transit officials spending some time on www.plainlanguage.gov.

“Maybe then Metro will see that clear communication is essential for helping customers accomplish their top tasks,” she wrote. “In this case, something as simple as catching a bus.”

Follow me on Twitter @postmetrogirl.