US President Donald Trump's midnight tweet contained a cryptic 'word' that made comedians out of many Twitter users.

At 12.06 am, the US President tweeted, 'Despite the constant negative press covfefe.'

Or, maybe it's 'covFEEF,' or 'covFEEFEE' - we're not quite sure. And neither is anyone else it seems.

Twitter users taking their best guess:

It's a new Pokemon character - notice the hair.

A popular ad slogan, as in, 'Switching to Geico could save you 15% or more on car covfefe.'

Or, the latest edition of TV show Survivor, 'coming next spring.'

One user claimed, 'Even the Queen is disturbed!'

Trump has since deleted the tweet so, sadly, it may forever remain a mystery... relegated to fodder for late-night TV hosts such as Jimmy Kimmel, who tweeted, 'What makes me saddest is that I'll never write anything funnier than 'covfefe.''

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