But chaat is what Indians have traditionally eaten between meals: after work, after school, on the way to the bus, at the beach. The word refers not to snacks in general, but to these specific mixes of crunch and salt with the classic toppings of yogurt, cilantro and tamarind. Chaats seem to have originated in Delhi, made from broken papadums (papri chaat). But Amita Kataria, a manager of the Bengali Sweet Shop in Jersey City, said, "Everyone in India, and Pakistan, too, now eats chaat." She said that the most popular chaats in New Jersey are the same as in India: pani puri, papri chaat and samosa chaat, for which she fries each samosa to order. (Many places simply microwave prefried samosas, which makes them both soggy and tough.)

All over India chaat wallahs, snack vendors, ply their trade from street carts or small storefronts. Like New York's hot dog vendors they are ubiquitous in parks, at train stations, in busy shopping streets. Chowpatty Beach in Mumbai (the former Bombay) is legendary all over India for the quality and variety of its chaats. Some chaats are light and crunchy, like an ethereally flavored snack mix, and others are practically lunch, like samosa chaat: piping hot samosas split open and covered with spicy chick peas, minced onion and cilantro, yogurt and tamarind. Chaats are mixed to your specifications (spicier, not so much cilantro, extra chickpeas), handed over on a banana leaf and devoured instantly.

"Chaats are like every flavor of chips and every kind of pizza you have here," said Dave Sharma, an owner of Amma, a Midtown restaurant, who is from Mumbai. "We eat chaat whenever we have a small hunger, but we will travel miles to get a good one. And people are loyal to their favorites."

Some legendary chaat wallahs, like Vital Bhelwala in Mumbai, have occupied the same space or patch of sidewalk for generations. Mumbai, and Mr. Bhelwala in particular, are famous for bhel puri, a puffed-rice chaat with bits of mint and potato. "We say that the flavor of the chaat is in the chaat wallah's hands," Mr. Sharma said. "And it's true, literally and figuratively."

Chaats can be made with almost anything crispy: fried bits of chickpeas, puffed rice, peanuts, browned mashed-potato patties, fresh ginger, mung bean sprouts and spice-dusted toasted lentils. Chaat masala usually includes amchoor, a tangy powder made from green mangoes, mint, cumin and pomegranate, but it must always include kala namak, a black salt with a pleasant whiff of sulfur, vital to chaat lovers.

Going for a chaat, Mr. Sharma says, is a social act with the same casual sociability as going for a beer. (Most Indians are Hindus and Muslims and drink little or no alcohol.) "After work a group of men will buy each other rounds of chaat on the way to the train and sometimes even have competitions over who can eat more." Piyush Sukhadia, an owner of chaat-and-sweet stores, said. "In India a guy might have a Mercedes and live in a house on a hill, but he still puts on his slippers and goes to eat chaat."

The word chaat means "to lick," in Hindi, said Mr. Sukhadia, whose family business was established in 1890, when his great-great-grandfather received the title of official sweetmaker to the nabob of Cambay in southern Gujarat. He said that although chaats used to be considered humble food with a taint of the street, it is now fashionable in India and here to offer a chaat station even at elegant weddings.

To that end Sandip Patel, the owner of Chowpatty Foods, one of the first chaat houses in the United States, has just imported a chaat cart from India in the red-and-white color scheme of the Chowpatty chaat wallahs. Chowpatty is the biggest chaat-and-sweet specialist in the Oak Tree Road neighborhood of Iselin, N.J., which lures thousands of Indian-Americans from as far away as Philadelphia and Boston to shop and snack every weekend. Oak Tree Road serves a knowledgeable clientele and has the best-quality sweets and chaats in the region: all the major manufacturers have shops there, and even amateurs like Shalimar and the Galaxy food court serve lively chaats with startlingly fresh flavors.

On Oak Tree Road you will see the ingredients for chaats divided in rows of stainless-steel bins, but a traditional chaat wallah sits surrounded by his mounds of dry ingredients and bowls of yogurt, chaat masala, cilantro or mint chutney and tamarind chutney and his own mix of jal-jeera, the "firewater" that is used to fill the habit-forming pani puri. "I just got back from India, and I was eating 60 or 70 pani puri a day," Mr. Patel said.

To me pani puri, with its explosive juices and racy flavors, was the most mind-altering chaat. A fine tribute to pani puri appears in a 1991 memoir about Mumbai by Ganghadar Gopal Gadgil. After several thousand words describing the process of eating and experiencing pani puri, he concludes with this tribute to the afterglow that, as I can attest, follows a pani puri binge:

"In that state of beatitude the Maharashtrians stop being surly, the Marwaris look at the millions of stars without being reminded of their own millions, the Sindhis admire the horizon without any intention of selling it, the Gujaratis speculate on the moon instead of the scrips they should have sold, the North Indians dream of things other than Hindi as the official language of the United Nations, and even the Parsi ladies stop nagging their husbands."