Japanese and foreign Twitter users were left scratching their heads Thursday after a tweet a day earlier by U.S. President Donald Trump made reference to the mysterious "covfefe."

Trump tweeted just after midnight in Washington on Wednesday: "Despite the constant negative press covfefe."

The tweet went viral instantly, becoming one the most popular posts of the divisive U.S. leader before it was deleted after nearly six hours online. Trump later cracked a joke at the post, tweeting around 6 a.m.: "Who can figure out the true meaning of 'covfefe' ??? Enjoy!"

While the Twitterverse was set alight with jokes and conspiracy theories, in Japan, too, confused English-language learners and bemused observers alike weighed in, offering some unique insights and tongue-in-cheek theories to illuminate the true meaning of Trump's typo, which was one of the top items trending on Twitter.

But most people were just befuddled.

"I have no idea what the intended form of covfefe is, but it seems that Trump mistyped — and a new vocabulary word burst onto the scene," Twitter user @nakashima1106 wrote Wednesday.

Others were incredulous.

“Never thought I’d see the day when Trump would make me laugh,” @aki23_6 wrote the same day.

Some saw a certain resemblance to Japanese politics.

User @t_kajiyama on Thursday said Trump's communication was reminiscent of former Prime Minister Taro Aso's penchant for making bizarre, inflammatory statements.

"Just like during the Aso administration, Trump tweets mysterious 'covfefe' tweet and sparks uproar," the tweet read.

Another user, @janjanj82785949, took a cryptographic approach and suggested that "covfefe" may be a portmanteau of "co" and "vivid," meaning "strikingly bright." "We should interpret this tweet as 'Despite the constant negative press, we're still brilliant,' " it read.

Meanwhile, the Twitter handle for dictionary publisher Merriam-Webster, known for its tongue-in-cheek musings on the SNS service, offered up a sarcastic tweet about people searching for the word on its website.

Then the tweet that launched a thousand internet memes was deleted, and Trump went back to the business of ripping into Democrats and "fake news" about the probe into Russia's meddling in the 2016 election, starting with his vanquished rival in last year's presidential election, Hillary Clinton.

"Crooked Hillary Clinton now blames everybody but herself, refuses to say she was a terrible candidate."

But Clinton countered the jab, joking that covfefe could have been "a hidden message to the Russians" during a technology conference Wednesday in Los Angeles.