T.S. Eliot first coined the phrase in his essay, 'The Metaphysical Poets' which was a literary criticism. The argument that he put forth was that cultivation of emotion and thought separately as divorced from one another was a broken way to deal with experiences that evoked both thought and emotion.
We may express the difference by the following theory: The poets of the seventeenth century, the successors of the dramatists of the sixteenth, possessed a mechanism of sensibility which could devour any kind of experience. They are simple, artificial, difficult, or fantastic, as their predecessors were; no less nor more than Dante, Guido Cavalcanti, Guinicelli, or Cino. In the seventeenth century a dissociation of sensibility set in, from which we have never recovered; and this dissociation, as is natural, was aggravated by the influence of the two most powerful poets of the century, Milton and Dryden (Eliot, "The Metaphysical Poets").
THERE IS NO UNION OF FEELING, EMOTION AND THOUGHT IN DISSOCIATION OF SENSIBILITY.WE FIND IT IN INDIAN POET AND POET OF VICTORIAN AGE.
It refers to the way in which intellectual thought was separated from the experience of feeling in seventeenth century poetry.