What is a imagism in literature?

Imagism was a poetic vogue that flourished in England, and even more vigorously in America, between the years 1912 and 1917. It was a revolt against the excesses of Romanticism and sought to restore the precise use of visual images to poetry. Prominent Imagists were T. E. Hulme, Ezra Pound, H. D. (Hilda Dolittle), John Gould Fletcher, Richard Aldington, Harriet Monroe, Amy Lowell, and William Carlos Williams. 

Their objectives were to use the language of common speech, to use only the exact word, to create new rhythms, to allow complete freedom of subject matter, to create concrete, hard-edged, sharply delineated images. 

The typical Imagist poem is written in free verse and undertakes to render as precisely and tersely as possible, and without comment or generalization, the writer's response to a visual object or scene, often the impression is rendered by means of metaphor or by juxtaposing a description of one object with that of a second or diverse object. Sylvia Plath was greatly influenced by the Imagists in writing her poems of the later period.