impressionism means to render life as it really seems to individual subjective experience. It fuses subjectivity of romancticism and objectivity of realism.

Lady windermere's fan is an impressionistic play
1) the atmosphere is dreamlike. It is preferred over the subject or the plot
theme and action are secondary to the general atmosphere of the play and changing moods of the characters. The imaginative coincidental scenes seem almost improbable to happen.
2) the subject matter is mundane -non-dramatic, casual, everyday life.
3)there is a deliberate use of ambiguity. The element of uncertainty and mysteriousness looms the play.
4) characterization is superficial. The characters have no psychological depth. The often look unreal.
5)keeping with the tradition of aestheticism, it doesnt aim at didacicism. There is no sharp criterion of right or wrong.
6) there is an involvement of spiritual element. An instance of sacrifice gives spiritual pleasure to the audience.
7)the character's personal desires are implicitly described. A character says long monologues, talking spontaneously about subjective and objective facts.