Naturalize, Perennialize, Bulbs
Every profession and hobby has its jargon. Sometimes words are loosely used and interchanged causing confusion to all. Naturalizing and perennializing bulbs are a good example.
Species tulips are a good example of perennializers. These tulips tend to grow and flower for multiple years. The Darwin hybrids, Emperor and triumph tulips are hybrids that also perennialize. These bulbs grow and return each year with only a modest amount of spread. Many of the showier hybrid tulips flower for only one or two springs partially due to their intolerance of the less-than-ideal bulb growing conditions.
Plants, including bulbs like daffodils, squills and grape hyacinths are often used for naturalizing. These bulbs return for many years and spread throughout the area. They reproduce readily by underground bulblets and above ground by seeds.
A bit more information: Bulbs used for naturalizing are usually planted in random patterns to appear as if nature planted them. Some gardeners scatter the bulbs and plant them where they land.