Shield money; commutation of service for a sum of money. See Escuage.

The sum that the holder of a knight's fee may pay his lord in lieu of military service. Sometimes used as a form of tax. (MEDIEV-L. Medieval Terms) Shield-tax, a tax paid in lieu of military service. (Gies, Joseph and Francis. Life in a Medieval Castle, 231) Feudal payment in place of knight service in the field. (Sayles, George O. The King's Parliament of England, 145) Literally "shield-money"; a payment in lieu of military service, paid in respect of the knights which a tenant-in-chief owed to the Crown. The personal obligation to serve of the tenant-in-chief himself could not be discharged by scutage, but only by fine. (Warren, W.L. Henry II, 636)

the money payment made instead of providing a knight or knights for knight service.

a tax levied in place of personal military service by VASSALs - a cash payment

from the Fr. ecuage and Latin scutum (shield), in the Middle Ages, payment made by enfeoffed knights and other feudatories to the Crown in lieu of military service; in some realms (such as the Kingdom of Sicily) the use of scutage continued into the nineteenth century as a means of taxing the nobility. See also oblation.

money taken from the knights by Henry I paid in lieu of the performance of military service. (p. 338)

The tax of scutage or escuage in the law of England under the feudal system, allowed a knight to "buy out" of the military service due to the Crown from the holder of a knight's fee. Its name derived from the knightly shield (in Latin: scutum). The term sometimes loosely applies to other pecuniary levies on the basis of the knight's fee.