When demonstrators first took to the streets to protest against the Turkish prime minister he branded them çapulcu, or looters. The word also means marauders or bums.

But Recep Tayyip Erdoğan's attempt to demean his opponents has backfired. Protesters in Istanbul and other cities have embraced the word as their own, labelling themselves proud çapulcu and even coining an English verb, capuling.

Pronounced chapulling, with the emphasis on the second syllable, it has become synonymous with the alternative, youth-driven anti-Erdoğan movement. Students sleeping under the plane trees in Gezi Park, Istanbul, have dubbed their makeshift camp Capulistan, with many mounting cardboard signs next to their dwellings that read "Capul residence". Meanwhile, the city's must-have fashion accessory is a white T-shirt with the slogan: "Every day I'm capuling".

A protester uses her mobile phone to publicise the clashes near Taksim in Istanbul. The word çapulcu has exploded across social media. Photograph: AFP/Getty

"Erdoğan called us çapulcu. It's an insult. It means you're a useless person, without a job, nobody," Kiraz Deniz Gurel, 30, a local musicologist, said. "But we're not losers. We really have good, good reasons for being here. We are young people and old people."

Gurel purchased the T-shirt for 7.5 Turkish lira – £2.50 and wore it for the first time on Monday. "Turkish people are very humorous. They love making jokes. It was John Lennon who said: 'When you give violence, you get back violence.' It's easy to respond with violence but humour is the better way. It means we are still alive, we are still human," she added.

The word has exploded across social media, which played a vital role in spreading news of the protests after state media failed to report them. Twitter users have adopted it as their own, adding the prefix çapulcu to their accounts. For example, "ilhan" becomes "çapulcu ilhan". The meme gained leverage after Erdoğan denounced the microblogging site as a curse and menace to society.

The 'Capul tree', adorned with small notes containing protesters' wishes, in Taksim Square. Photograph: Thomas Campean/Rex Features

And those whose job it is to explain this citizens' revolt have used the phrase as well. The Zaman newspaper described the protests as "Turkey's 'capuling' movement". Its columnist, Arzu Kaya Uranli, noted: "The whole world is witnessing something exceptional for Turkish history. The Gezi Park protests have become an amazing civil movement in Turkey … rather than rejecting the humiliating and hurtful label of looters, protesters embraced it in an artistic way and applied it to their activism."

She defined capuling as "to act in a peaceful and humorous manner to remind governments why they exist".

The park and next-door Taksim Square have their own Capul art gallery – paintings by protesters hung on concrete walls. There is also an impressive Capul peace tree made from bits of fencing and stumps ripped up by government bulldozers after teargas-wielding riot police moved in. Istanbul residents have stuck hundreds of wishes on the tree, calling for anything from world peace to Erdoğan's resignation.

A march in Milan in solidarity with Occupy Gezi. The slogan 'Resistanbul' has also gained ground. Photograph: Marco Busato/Demotix/Corbis

After two weeks of protests the entire square and surrounding side streets have been daubed with humorous graffiti, including: "Stop Istanbullying!", "Gas me baby one more time", "In Gezi we trust", and "I know the rules but the rules don't know me". On nearby wasteland someone spray-painted: "Have you ever capuled so much, you thought you would faint?"

Polen Budak, 23, the fine art student who built the Capul tree, said: "The creativity is incredible. It's all very spontaneous. We've been sleeping only three or four hours a night but we are full of energy.

"It's very degrading to call us looters. In fact, it was Erdoğan and his supporters who looted the city's green spaces and took them from us. People fought back with great humour. They took the insult and they owned it."