noun

• An English habitational surname from Old English [[Unsupported titles/`lsqb`æt#Old English|[æt]] þǣre] sīdan īeġe (“[at the] wide island”).
• A male or female given name transferred from the surname.
• A locale in Canada.
• A town in British Columbia; named for nearby Sidney Island, itself for Royal Navy hydrographer Frederick W. Sidney.
• A community in North Norfolk municipality, Manitoba.
• A locale in the United States:
• A town in Arkansas.
• A village in Illinois.
• A town in Indiana.
• A city, the county seat of Fremont County, Iowa; named for Sidney, Ohio.
• An unincorporated community in Kentucky.
• A town in Maine; named for Philip Sidney.
• An unincorporated community in Missouri.
• A city, the county seat of Richland County, Montana; named for Sidney Walters, a 6-year-old early settler.
• A city, the county seat of Cheyenne County, Nebraska; named for railroad executive Sidney Dillon.
• An unincorporated community in New Jersey.
• A town and village therein, in Delaware County, New York; named for British naval officer Sidney Smith.
• A city, the county seat of Shelby County, Ohio; named for English poet Philip Sidney.
• An unincorporated community in Texas.
• An unincorporated community in West Virginia.
• An unincorporated community in Wisconsin.
• (Cambridge University slang) Clipping of Sidney Sussex College, Cambridge.