verb

• (transitive) To cut down or reduce.
  "O conſider my caſe, moſt blisfull Queen, […] Diſpell thoſe Clouds which hover 'twixt my King and his higheſt Counſell, […] that my great Law-making Court be forced to turn no more to polemicall Committees, […] but that they may come again to the old Parliamentary Rode, To the path of their Predeceſſours, to conſult of means how to ſweep away thoſe Cobwebs that hang in the Courts of Juſtice, and to make the Laws run in their right Channell; to retrench exceſſive fees, and finde remedies for the future, that the poor Client be not ſo peeled by his Lawyer, and made to ſuffer by ſuch monſtrous delays, that one may go from one Tropick to the other, and croſſe the Equinoctiall twenty times, before his ſute be done; […]"
• (transitive) To cut down or reduce.
  "This section prescribes that an employer shall ordinarily retrench the workman who was the last person to be employed in that category, unless for reasons to be recorded in writing, the employer retrenches any other workman."
• (transitive) To confine; to limit; to restrict.
  "They say of God—That He spreadeth forth the heavens as a tent to dwell in; and that as a garment, some time hence, He shall roll them together. These figures, ought they then to receive a retrenched interpretation? Ought they to be denuded of their oriental garb? Not so, […]"
• (transitive, military) To furnish with a retrenchment (a defensive work within a fortification).
  "to retrench bastions"

verb

• (transitive) To dig or redig a trench where one already exists.
  "The [fishing] technique was to clear the channel downstream from the lagoon for about twenty to forty yards, but not all the way to the salt water. A small "bridge" was left at the lower end of the lagoon. When holding pits had been dug near the end of the re-trenched channel and everyone was ready, the "bridge" was dug out and the outrush of water brought hundreds of fish along with it."