To or towards the left side; to the left of (a line, plane, etc.). Contrasted with "dextrad [adjective]".
Directed or moving towards the left. Contrasted with "dextrad [adjective]".
Early 19th century; earliest use found in John Barclay. From classical Latin sinistra left hand, use as noun (short for manus sinistra left hand) of feminine of sinister sinister + -ad.