We found 2 dictionaries that define the word black as Newgate's knocker:

General (1 matching dictionary)

1. black as Newgate's knocker: Wiktionary

Slang (1 matching dictionary)

2. black as Newgate's knocker: English slang and colloquialisms used in the United Kingdom

Definitions from Wiktionary (black as Newgate's knocker) ▸ adjective:  (UK, simile) Completely black in colour. ▸ Words similar to black as Newgate's knocker ▸ Usage examples for black as Newgate's knocker ▸ Idioms related to black as Newgate's knocker ▸ Wikipedia articles (New!) ▸ Popular nouns described by black as Newgate's knocker ▸ Words that often appear near black as Newgate's knocker ▸ Rhymes of black as Newgate's knocker ▸ Invented words related to black as Newgate's knocker