A midnight tweet from U.S. President Donald Trump has social media trying to find a meaning in the mysterious term “covfefe”.

Mr. Trump tweeted just after midnight Eastern time (around 9.30 a.m. IST) on Wednesday: “Despite the constant negative press covfefe.”

The tweet immediately went viral and became one of the President’s more popular posts.

At 2.40 p.m. IST Mr. Trump’s “covfefe” tweet had more than 120,000 retweets and had been shared 39,000 times, according to Twitter figures.

Then, around 3.15 p.m. IST, more than five hours after it was posted, the mysterious tweet vanished.

Soon after Mr. Trump himself joined the deciphering game. “Who can figure out the true meaning of “covfefe” ??? Enjoy!” he tweeted, in an unusual display of self-deprecating humour.

Who can figure out the true meaning of "covfefe" ??? Enjoy! — Donald J. Trump (@realDonaldTrump) 31 May 2017

Many on Twitter have supplied tongue-in-cheek meanings. One user joked that “covfefe” is already a popular name for babies in States that voted for Mr. Trump.

Dictionary publisher Merriam-Webster checked in with an eye-rolling tweet about people looking up “covfefe” on its website.

Dozens of definitions have been submitted the Urban Dictionary website, which crowdsources meanings for slang terms.

Was it an acronym? A secret message? Or just a typo?

Wags around the world weighed in with biting sarcasm, and #covfefe quickly became the top trending item on Twitter.

Comments included a mock Google translation of “covfefe” from Russian into English as “I resign,” and comments like “Drain the covfefe” — a play on Mr. Trump’s promise to “drain the swamp” in Washington.

“’Covfefe is a great word, period! — Sean Spicer tomorrow,” read one tweet, mentioning the President’s spokesman.

To avoid confusion, the Regent’s English Language Centre in London wrote: “To all of our English language students, we can confirm that ‘covfefe’ is not an English word. Yet.”

The President returned to his normal Twitter routine later in the morning by slamming Democrats over the probe into Russia’s meddling in the 2016 election.

Since entering office, Mr. Trump has used Twitter to issue declarations on everything from Arnold Schwarzenegger’s TV performance to an alleged “MASSIVE trade deficit with Germany”.