Dissociation of sensibility is T. S. Eliot's term for the split he believed had developed in English poetry between intellectual thought and emotional feeling. He argued that, after the Metaphysical poets, poets increasingly lost the ability to unite ideas, sensations, and emotion in a single, fully integrated style.
The phrase is mainly used in discussions of literary history and criticism, especially when comparing later poetry with the Metaphysicals.
Example
A critic might say that a later poet shows dissociation of sensibility when the poem argues cleverly about love but never lets the feeling of love come through in the language.