Meaning

• To loosen, as something interlaced or knotted; to disengage the parts of.

  "to untie a knot"

• To free from fastening or from restraint; to let loose; to unbind.

• To resolve; to unfold; to clear.

• To become untied or loosed.

• In the Perl programming language, to undo the process of tying, so that a variable uses default instead of custom functionality.