From loose + -en.

• (British) IPA: /ˈluːsn̩/

loosen (loosens, present participle loosening; simple past and past participle loosened)

1. (transitive) To make loose.

   Synonyms: ease, relax, untighten

   to loosen a knot; to loosen one's grip / hold on something

   After the Thanksgiving meal, Bill loosened his belt.

   • 1626, Francis Bacon, Sylva Sylvarum: or A Naturall Historie, London: William Lee, Century 5, p. 111,

     […] after a yeares Rooting, then Shaking doth the Tree good, by Loosening of the Earth […]

   • 1992, Michael Ondaatje, chapter 10, in The English Patient‎, London: Picador, published 1993, page 265:

     His days at the villa had loosened his body and freed his tenseness […]

2. (intransitive) To become loose.

   I noticed that my seatbelt had gradually loosened during the journey.

   • 1764, Oliver Goldsmith, An History of England, in a Series of Letters from a Nobleman to his Son‎, London: J. Newbery, Volume 2, Letter 19, p. 159:

     The sea scurvy is attended with an universal putrefaction, the teeth loosen, old wounds that had been healed again open […]

   • 1940, Richard Wright, Native Son‎, London: Jonathan Cape, published 1970, Book 3, p. 387:

     Max caught Bigger’s shoulders in a tight grip; then his fingers loosened and he sank back to the cot […]

3. (transitive) To disengage (a device that restrains).

   Synonyms: undo, unfasten

   • 1994, J. M. Coetzee, chapter 6, in The Master of Petersburg‎, New York: Viking, page 55:

     Her hair is drawn back under a heavy enamelled clasp. He loosens the clasp and lays it on the table.

4. (intransitive) To become unfastened or undone.
5. (transitive) To free from restraint; to set at liberty.

   Synonyms: liberate, release, set free

   • 1876, George Eliot, Daniel Deronda‎, Book 1, Chapter 8:

     I thought you had more sense than […] to suppose that because you have fallen into a very common trouble, such as most men have to go through, you are loosened from all bonds of duty […]

   • 1905, Edith Wharton, The House of Mirth‎, Book 2, Chapter 11:

     The recollection loosened a throng of benumbed sensations—longings, regrets, imaginings, the throbbing brood of the only spring her heart had ever known.

6. (transitive) To relieve (the bowels) from constipation; to promote defecation.
   • 1626, Francis Bacon, Sylva Sylvarum: or A Naturall Historie, London: William Lee, Century 1, p. 14,

     […] Feare looseneth the Belly; because the Heat retiring inwards towards the Heart, the Gutts and other Parts are relaxed;

   • 1646, Thomas Browne, Pseudodoxia Epidemica‎, London: E. Dod, Book 2, Chapter 3, p. 73:

     […] omitting the vehicle of water and honey, which is of a laxative power it selfe, the powder of some Loadstones in this dose doth rather constipate and binde, then purge and loosen the belly.

7. (transitive, obsolete) To create a breach or rift between (two parties).
   • c. 1603–1606, William Shakespeare, “The Tragedie of King Lear”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC ↗, [Act V, scene i]:

     I had rather lose the battle than that sister
     Should loosen him and me.

8. (intransitive, obsolete) To sail away (from the shore).

   Synonyms: put out

   • 1565, Arthur Golding, transl., The Eyght Bookes of Caius Iulius Cæsar conteyning his martiall exploytes in the realme of Gallia and the countries bording vppon the same‎, London: William Seres, Book 4:

     […] after the .iiii. day of oure arryuall in Britayne, the eightene shyps that we spake of before, which hadde the horsemen to conuey ouer, loosened from the further hauen with a soft wynd.

• tighten

• loose
• unloosen

• French: desserrer
• German: lösen, lockern
• Italian: allentare
• Portuguese: afrouxar
• Russian: ослабля́ть
• Spanish: aflojar, soltar

• Portuguese: soltar, liberar, libertar