Dregs are the sediments or lees that settle at the bottom of wine or other liquor. The word may also represent a bowl or cup in one passage, but its clearest literal sense is the sediment remaining after liquid has stood.
Psalm 75 portrays the wicked as drinking the cup of divine wrath to its dregs, meaning that they receive judgment to the last drop. Isaiah uses the image of the cup of trembling and fury.
The Revised Version changes “dregs” to “bowl” in Isaiah 51:17, 22, where the underlying word means bowl or chalice. In Psalm 75 the Hebrew term specifically denotes sediments or wine lees.