This is not a pleonasm as all the parts in the expression are necessary to understand the concept. In fact, Merriam-Webster has a definition for “shut down (http://www.merriam-webster.com/dictionary/shut%…). “Shut down” is used to indicate the termination of a process. For instance, a running machine or computer. This expression would become a pleonasm when used with some nouns that are inherently closed (shut) when in the “down” position, such as certain curtains or blinders. For example, “shut down the blinder.”
pleonasm: 1. the use of more words than are necessary to express an idea; redundancy. 2. an instance of this, as free gift or true fact. 3. a redundant word or expression.
