The phrase relates to the iconic image of a lone protester standing before tanks in China’s Tiananmen Square during demonstrations in 1989.
On Friday users who searched for the term reported receiving the message: “There are no results for tank man”.
It prompted accusations of possible censorship on the protest anniversary.
“Tank Man” is often used to describe a man, who had never been identified, pictured standing before tanks in Tiananmen Square in June 1989. It became the defining image of the crackdown in which hundreds, possibly thousands, were killed.
But when users in countries including the UK, US and Singapore tried to find the image on Friday, the 32nd anniversary of the protests, it appeared to have vanished.
China heavily censors any online discussion about the Tiananmen Square crackdown. This year commemorations marking the anniversary in Hong Kong were low key after authorities banned a vigil.
Beijing is known to require search engines operating in its jurisdiction to censor results, but those restrictions are rarely applied elsewhere.