From natural wonders like Yellowstone to man-made treasures like the Space Needle, the U.S. isn't called America the Beautiful for nothing. Here is the most iconic landmark in every US state.
Si /si/ [1 syll.] as a name for boys. Si's name origin is Hebrew, and Si means to hear, listen; reputation. Si is an alternate spelling of Simon (Hebrew). Compare last name Sei.
SI unit any unit of the International System of units (the metric system); see also si units. step-down unit a nursing unit designated to provide care for patients who are stable enough to be discharged from the intensive care unit but are not yet ready to be cared for on a medical-surgical unit.