A slim volume chronicling the slang used on the streets of Tehran has become an unlikely bestseller.
There are strict rules governing mixed-sex conduct in Iran
The Persian Dictionary of Argot began as an academic study of new vernacular words in Farsi.
But its unravelling of code words used by Tehran's youth to circumvent social strictures has gripped parents, Iranian literary circles and the young alike.
It is now in its sixth edition, yet remains almost impossible to find in Tehran bookshops, visitors report.
Many code words devised by the street-savvy youth in Tehran relate, unsurprisingly, to the opposite sex.
Public contact between Iranian girls and boys is forbidden, so phone numbers are often furtively exchanged as youths drive around in single-sex vehicles.
And young Iranian men compare notes on the women they encounter using - rather chauvinistic - car metaphors, the dictionary reveals.
Iranian street slang
"Zero kilometre": virgin
"Overturned car": non-virgin
"Been in an accident": girl who is pregnant
A "zero-kilometre" is a virgin, while
an "overturned car" is a non-virgin.
A person's rear is alluded to with the word "hubcap", while legs are referred to as the "axle", reports the London Times.
A measure of ridicule is also reserved for some makes of cars, with an Iranian-made Peugeot 405 referred to as a "peasant bride".
'Want to be different'
Analysts have expressed surprise that the book got past censors at Iran's Ministry of Culture and Islamic Guidance virtually unchanged.
One suggested the book's approval could have been a last defiant act by the reformist government of Mohammad Khatami before a conservative regime takes over.
But another Iran watcher told BBC News Online the book was not highly subversive, but simply testified that - like youths all over the world - Tehran's teenagers want to create their own subcultures.
"They don't use slang because they're not allowed to be different, but because they want to be different," she said.