Unbend v. t. : To free from flexure; to make, or allow to become, straight; to loosen; as, to unbend a bow.

Unbend v. t. : A remit from a strain or from exertion; to set at ease for a time; to relax; as, to unbend the mind from study or care.

Unbend v. t. : To unfasten, as sails, from the spars or stays to which they are attached for use.

Unbend v. t. : To cast loose or untie, as a rope.

Unbend v. i. : To cease to be bent; to become straight or relaxed.

Unbend v. i. : To relax in exertion, attention, severity, or the like; hence, to indulge in mirth or amusement.

Example:
How do you Unbend a bent plastic lip made of Polyurethane?

Taxonomy
Merriam-Webster Online Dictionary, Dictionary, webster, Word Games, Webster Online Dictionary with audio pronunciations, thesaurus, Google Search, glossary, english, language, ESL, Search, Inflected, 13th century, transitive verb, flexure, bow, sail.

Defination from the web:
unbend from the Merriam-Webster Online Dictionary with audio pronunciations, thesaurus, Word of the Day, and word games. ... transitive verb 1 : to free from flexure : make or allow to become straight <unbend a bow> 2 : to cause (as the mind) to relax ...