Verbal contraption is a phrase sometimes used to describe a poem as a carefully made verbal mechanism rather than a spontaneous outpouring. It suggests that the poem is built from language, structure, sound, and pattern working together, with each part doing a specific job.
The phrase is closely associated with W. H. Auden, and it is not a standard technical term in the way that sonnet or enjambment is. Because of that, it is best treated as a descriptive label for a crafted poem, not as a fixed verse form.
Example
A dozen neat lines click into place,
turning image, rhyme, and pause
like gears inside a small brass clock.