transitive verb unbent -·bent′ or unbended -·bend′ed, unbending -·bend′·ing

1. to release (a bow, etc.) from strain or tension
2. to relax (the mind) from strain or effort
3. to straighten (something bent or crooked)
4. Naut.
   1. to loosen or unfasten (a rope, sail, etc.)
   2. to untie (a rope)

Etymology: ME unbenden: see un- & bend

intransitive verb

1. to become straight or less bent
2. to become free from constraint, stiffness, or severity; relax and be less formal, more natural, etc.