vers libre (n.)

1902, from French, literally "free verse," lines of varying length.

I remarked some years ago, in speaking of vers libre, that 'no vers is libre for the man who wants to do a good job.' The term, which fifty years ago had an exact meaning in relation to the French alexandrine, now means too much to mean anything at all. [T.S. Eliot, introduction to "Selected Poems of Ezra Pound," 1928]