👉 Expanse is a Greek word meaning "to stretch" in the Old Testament, often used to describe large amounts of land or sea. It implies going beyond or exceeding the capacity for a given amount. Definition: Expanse means to stretch out or extend over vast areas or lengths of time. For example, if one was to say that it was "expanse of the stars" they are referring to the total number of stars in our Milky Way galaxy, which is estimated to be around 90 billion.