If you untie something such as string or rope, you undo it so that there is no knot or so that it is no longer tying something. She hurriedly untied the ropes binding her ankles Then she untied her silk scarf
If you untie something that is tied to another thing or if you untie two things that are tied together, you remove the string or rope that holds them or that has been tied round them. Nicholas untied the boat from her mooring Just untie my hands
When you untie your shoelaces or your shoes, you loosen or undo the laces of your shoes. She untied the laces on one of her sneakers Your boot lace is untied. = undo. to take the knots out of something, or unfasten something that has been tied