"Unusual size" is a phrase that can be used to describe something that is not the usual or expected size. For example:

"I couldn't find my size in this store, but they had a shirt in an unusual size that fit me perfectly." (这家商店没有我的尺码，但他们有一件不寻常尺寸的衬衫刚好合身。)

"The dinosaur fossils we found were all unusual sizes. Some were much larger than any we had seen before." (我们发现的恐龙化石都是不寻常尺寸。有些比我们之前看到的要大得多。)

The phrase "unusual size" comes from the adjective "unusual," which means not usual or expected, and the noun "size," which refers to the dimensions or proportions of an object. The phrase is commonly used to describe objects or things that are not the standard or typical size for their category.