Westerner's close-up on Geisha; Geisha, by Liza Crihfield Dalby. Berkeley: University of California Press. 347 pp. $25.

There are single words that somehow suggest, at least to the imagination's fancy, the cultural sweep of a land. ''Cowboys'' is arguably one of those words. ''Geisha'' most certainly is another. For the Westerner, the word summons up a host of cultural images and intrigues; in fact, with the exception of latter-day associations evoked by ''Sony'' and ''Toyota,'' geisha may be the one word that - for an outsider - captures the essence of things Japanese.

Which is not to say that most Westerners know what a geisha actually is. Generally, it seems, the fuzzy notion that prevails is of a high-class, artistically inclined prostitute. For anyone interested in having that fuzzy notion set straight, ''Geisha'' is a delightful find - an insider's look at the ''flower and willow'' world, written by a Westerner.

Liza Crihfield Dalby set out to study the geisha of Japan as a graduate student in anthropology. She wound up by actually becoming a geisha during her year-long stay in Kyoto - the only time a non-Japanese has ever been accepted into those elite ranks.

Her book is both enlightening and engaging - written with a uniquely informed sensitivity that keeps its scholarly nature from becoming staid. In exploring the microcosm of geisha society, she ranges intelligently across many broader sections of Japanese culture, from history to relations between men and women.

The geisha profession emerged in the 18th century, when geisha served as entertainers for licensed prostitutes and their customers. Although geisha take lovers rather than marry (the roles of wife and geisha are mutually exclusive in Japan), they are traditionally highly disciplined artists - not exotic prostitutes. ''Gei,'' in fact, means ''art.'' Dalby does not apply any feminist reasoning here. But in exploring the geisha and their world, she succeeds remarkably well.