The Collaborative International Dictionary of English v.0.48:

Rescous \Res"cous\ (r?s"k?s), n. [OE., fr. OF. rescousse, fr.
   rescourre, p. p. rescous, to rescue. See Rescue.]
   1. Rescue; deliverance. [Obs.] --Chaucer.
      [1913 Webster]

   2. (Law) See Rescue, 2. [Obs.]
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

RESCOUS, crim. law, torts. This word is used synonymously with rescue, (q.v.)
and denotes the illegal taking away and setting at liberty a distress
taken, or a person arrested by due process of law. Co. Litt. 160.
     2. In civil cases when a defendant is rescued the officer will or will
not be liable, as the process under which the arrest is made, is or is not
final. When the sheriff executes a fi. fa. or ca. sa. he may take the posse
comitatus; Show. 180; and, neglecting to do so, he is responsible; but on
mesne or original process, if the defendant rescue himself, vi et armis, the
sheriff is not answerable. 1 Holt's R. 537; 3 Eng. Com. Law Rep. 179, S. C.
Vide Com. Dig. h.t.; Yelv. 51; 2 T. R. 156; Woodf. T. 521 Bac. Ab. Rescue,
D; Doct. Pl. 433.