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Webster 1828 Edition

ppr.

Freeing from tightness, tension or fixedness; rendering less compact.

loosening

loosening ‎(plural loosenings)

The act of making something looser.
- 2013, Michael Scott, Religious Language (page 169)
  Turning to metaphor, the loosenings involved in metaphorical interpretation tend not to be pure but to involve a change that results in the extension of the loosened concept overlapping with but not including all of the denotations of the pre-loosened concept.