Definitions
1.nounGround ploughed and harrowed but left unseeded for one year.
2.nounUncultivated land.
3.nounThe ploughing or tilling of land, without sowing it for a season.
4.adjective(of agricultural land) Ploughed but left unseeded for more than one planting season.
5.adjective(of agricultural land) Left unworked and uncropped for some amount of time.
6.adjectiveInactive; undeveloped."a fallow period in one's career"