This broadening incident from an all-too-broadening life occurred, as most of life seems to, in a station wagon. On a typical Saturday in autumn or spring, the highways in suburban Maryland are congested with station wagons--Democrats in Volvos, young players, male and female, to and from soccer games.

A parent tough enough to keep his or her ears open gets a shattering sense of the mind and vocabulary of the nation's 9-year-olds. It confirms the proposition that Mowgli, the boy raised by wolves in Kipling's "Jungle Book," is not really unlike children raised by normal parents, who are members of a different species.

Recently, the Will wagon, brimful of the anarchy that 9-year-olds secrete, was inching through coagulated traffic opposite a shopping center where a movie marquee announced: "The Last Virgin in America (R)." Now, it is a well-documented fact that the average child who is blind as a brussels sprout when looking for the sneaker he left in the middle of the living room can read a movie marquee that is still over the horizon, especially if the movie being advertised has received the tantalizing accolade of an "R" rating.

On this occasion, the 9-year-old culture critics said: "The Last Virgin in America'--Ohoooooooo." And the driver thought: Arrrggghhhh--what is the decorous thing to say when one of the creatures asks what a virgin is and why America is down to its last one?

The Shorter Oxford English Dictionary (no station wagon should be without one) offers a useful salad of definitions that could have been given to the soccer players. One definition is: "A female insect producing fertile eggs by parthenogenesis." The soccer players would not have been satisfied with that.

Another definition is "Of a fortress city, etc., that has never been taken or subdued." The OED gives this example: "In Africa, the highest mountain is still a virgin." That is, surely, a retrograde use of the word, because it suggests that sex is a conquest, a form of aggression. Nine-year-olds of my acquaintance, of both genders, should not be told that there are unexplored fields for their overflowing aggressions.

The first OED definition is charged with theology: "An unmarried or chaste maiden or woman, distinguished for piety or steadfastness in religion." The second definition is similar, but the third is: "A young woman or maiden of an age and character affording presumption of chastity." That raises more problems than it solves, because the average driver of a station wagon boiling with 9-year-olds does not want to conduct a conversation on the admittedly fascinating question of at what age, in 1983, the presumption referred to evaporates.

I have asked other parents what they would have said about what a virgin is. One father suggests: "Tell them a virgin is a girl without a boyfriend." But that definition postulates a correlation that is dubious--and defeatist. Anyway, the OED is not so sexist as to say a virgin must be female. Its fifth definition is: "A youth or a man who has remained in a state of chastity."

Perhaps as the traffic crept along I should have fallen back on the last resort, the truth. Perhaps I should have said the idea of virginity has to do with sexual intercourse. But a station wagon is no place for a sex-education seminar.

Some occasions call for all that the brain can manage in the way of circumlocutions. I have always admired the character who mastered the use of the triple negative, as in the phrase "not unmeaningless." Slip that labyrinth of a phrase into a conversation and it will swallow up the conversation, setting you free from tiresome talk. But circumlocutions and ruses were not so necessary back when movie marquees caught children's attention with titles like "Comanche Comeuppance."

Nothing is more striking to this parent than how early and strongly children feel the pull of popular culture. Today the social atmosphere is heavily dosed with invitations to think about what are loosely called adult topics. But, fortunately, the average 9-year- old cannot think about anything for very long.

So when one of them said, "What's a virgin?" I answered by shouting, "Chuck E. Cheese's (a pizza emporium and games arcade) coming up on the right!" The answer was, I know, a bit oblique, and perhaps a dereliction of duty. But some of life's duties should be left for those occasional intervals when one is not in a station wagon.