Limited Edition refers to items that are available for purchase in the Market or for Gifting, but only for a limited amount of time. Most Limited Edition items will be available for a few days to a few weeks, depending on the item or the event that is hosting the item.
Currently, some Pioneers have been having difficulties with normal gift items (e.g. building materials and food) being treated as expired Limited Edition gifts. Zynga has not yet acknowledged this bug.