Dregs are the sediment at the bottom, or the worst of something. The dregs of the bottle, drain the dregs, the dregs of society.
It is plural only. In wine the sediment is natural and is why a bottle is decanted, and in coffee it is grounds. The figurative use is one of the ugliest phrases in English and says more about the speaker than about anybody described.
1noundregsThe sediment at the bottom, or the worst of something.
“He drank his coffee down to the dregs and asked for another cup.”
dregs is a sediment.
Practised in A Song of Ice and Fire