It may be that we use the word "supernatural" all too loosely.
St. Thomas Aquinas (1225 - 1274) made a three-fold distinction between the categories of natural, preternatural, and supernatural which I think is helpful. In his morphology, the latter term should be restricted exclusively to such occurrences that God alone can perform by divine fiat. By too loosely blending these categories, we have lost the middle category of the preternatural.
Here's a very simple explanation of how he broke this down:
Natural: The natural world incorporates that which takes place normally, under usual, and expected conditions. If I throw a rock into the air, it naturally comes down. If an apple falls from a tree, it tends to rot (or sprout a seedling!). If I throw a piece of iron into the lake, it sinks.
Preternatural: Preternatural occurrences are those that take place under extraordinary circumstances but are nevertheless explainable by other created agents. This includes angels and demons. In medieval theology, the preternatural world was ubiquitously assumed. Angels, demons, spirits, and even non-Biblical entities (think: wood fairies!) were considered regular (even if mysterious) causal agents involved in everything from sudden illnesses, to housefires, to stolen horses. Through the days of the Salem Witch Trials and beyond, the preternatural world was taken for granted. Cotton Mather's book Wonders of the Invisible World is literally the "textbook" on such fantastical accounts.
Supernatural: Supernatural acts then, are those occurrences that only God Himself can perform. Creation ex nihilo, breathing life into the dust of the ground, the regeneration of the sinful human heart, and the resurrection of the dead are quintessential examples of occurrences that technically fall under this later, more restricted category. Since not even angels and demons can perform such wonderous feats, they are by definition supernatural (above any created agent).
For more on this topic, check out my video breakdown of this three-fold distinction using the resurrection of Jesus Christ (Matthew 28:1-10) and the angelic appearance at the tomb as a Biblical example illustrating all three categories.