1) Knowing. Understanding another's meaning. The swell was flash, so I could not draw his fogle. The gentleman saw what I was about, and therefore I could not pick his pocket of his silk handkerchief. To patter flash, to speak the slang language.
See patter.
2) A periwig. Rum flash; a fine long wig. Queer flash; a miserable weather-beaten caxon.
to flash
To shew ostentatiously. To flash one's ivory; to laugh and shew one's teeth. Don't flash your ivory, but shut your potatoe trap, and keep your guts warm; the Devil loves hot tripes.
a supply of water from the locks on the Thames, to assist the barges. S. Any little pool. North. ...
A glossary of provincial and local words used in England by Francis Grose
To fail of success. A metaphor borrowed from a gun, which, after being primed and ready to be discha...
Dictionary of American Words And Phrases by John Russell Bartlett.