- Proper noun. Old name of a city in modern Israel famed from the Crusades: see Acco.
- Proper noun. A state in north-western Brazil, bordering Peru and Bolivia.
- Proper noun. (surname) .
- Noun. (obsolete) A field.
- Noun. A unit of surface area (''symbol'' a. ''or'' ac.), originally as much as a yoke of oxen could plough in a day; later defined as an area 1 chain (22 yd) by 1 furlong (220 yd), or 4,840 square yards. Equivalent to about 4,046.86 square metres.
- Noun. (in the plural, informal) A large amount (of area).