acre foot

Short definition from Wiktionary

Noun

1. 1
   A unit of measure, used for volumes of water, equal to one acre times one foot (that is, to the amount of water required to cover one acre of land to a depth of one foot), which is 43,560 cubic feet, 325,851 gallons, 1,233 cubic meters.
2. 2
   A unit of volume equal to an acre times a foot, equal to 43,560 cubic feet, or about 1233.5 cubic meters.