To cast loose or untie
To remove a bend so as to make, or allow to become, straight.
To cease to be bent; to become straight.
To relax in exertion, attention, severity, or the like
To release (a load) from a strain or from exertion; to set at ease for a time; to relax.
To unfasten sails from the spars or stays to which are attached for use.
to undo, untie, or open or become undone, untied, or opened.
Somehow she managed to unsnib the window and escape.