What is the definition of dregs?

Answer 1

The last little bit of something that isn't necessarily desirable like the last little bit of tobacco crumbs in the bottom of a pouch or the last little bit of your cold cup of tea

residue, sediment, silt

Answer 2

The last liquid found in a cup, bottle or barrel, sometimes called the lees. When you have almost finished your cup of coffee, the last few sips are the dregs of the cup. As the dregs are likely to contain the most sediment and other impurities, they are the worst part of the cup, bottle or barrel, and hence "dregs" is used figuratively for "the worst part."