What does “grandfathered” mean?

Grandfathered is another way to describe something that is considered existing and nonconforming. Grandfathered or existing non-conforming is a term used to describe a situation that existed prior to the adoption of a new ordinance or law. For example: A resident has a 48 inch high fence in their front yard which was constructed 10 years ago. The neighbor desires to construct the same fence in their front yard, but a new ordinance was passed three years ago which still permits a fence in the front yard, but only 42 inches high. The 48 inch high fence is “grandfathered” because it existed prior to the adoption of the new height limitation.