great: far above the ordinary measure of its kind, whether in size, force, amount, or importance
One word covers a whole family of bigness. It can measure a thing in space (a large stone, a high mountain, a wide chasm), or in force and degree (a violent storm, a loud cry, deep fear and joy), or in worth and standing (a great prophet, the greatest in the kingdom, the great city Babylon). The thread running through all of these is the same: something stands far above the normal measure of its kind.
Which kind of greatness is meant comes from what the word is describing, not from the word itself. Said of a rock it means heavy and large; said of a voice it means loud; said of a wind it means strong; said of a person it means important or highly ranked; said of a day or a sign it means weighty and significant. Greek listeners heard one idea and let the setting fix the measure, so the senses below are facets of a single adjective rather than separate words.
The same word also does the work of "greater" and "greatest" when its endings change, so it carries the New Testament's running argument about who ranks highest, from the disciples quarreling over status to Jesus naming the first and great command. The greatness in view is often turned upside down: the one who would be great must serve.