The Collaborative International Dictionary
Knight's fee \Knight's fee\ (Feudal Law) The fee of a knight; specif., the amount of land the holding of which imposed the obligation of knight service, being sometimes a hide[1](b) or less, sometimes six or more hides.
Wikipedia
In feudal Anglo-Norman England and Ireland, a knight's fee was a unit measure of land deemed sufficient to support a knight. Of necessity, it would not only provide sustenance for himself, his family, esquires and servants, but also the means to furnish himself and his retinue with horses and armour to fight for his overlord in battle. It was effectively the size of a fee (or "fief" which is synonymous with "fee") sufficient to support one knight in the ongoing performance of his feudal duties ( knight-service). A knight's fee cannot be stated as a standard number of acres as the required acreage to produce a given crop or revenue would vary depending on many factors, including its location, the richness of its soil and the local climate, as well as the presence of other exploitable resources such as fish-weirs, quarries of rock or mines of minerals. If a knight's fee is deemed co-terminous with a manor, an average size would be between 1,000 and 5,000 acres, of which much in early times was still "waste", forest and uncultivated moorland.
Usage examples of "knight's fee".
Inordinately flattered that his simple knight's fee holdings should be so honored as to be the secret repository of royal possessions, the knight had solemnly oathed himself and his heirs to honor the commands of his king.