The Collaborative International Dictionary of English v.0.48:

King's Bench \King's Bench\n. (Law)
   Formerly, the highest court of common law in England; -- so
   called because the king used to sit there in person. It
   consisted of a chief justice and four puisne, or junior,
   justices. During the reign of a queen it was called the
   Queen's Bench. Its jurisdiction was transferred by the
   judicature acts of 1873 and 1875 to the high court of justice
   created by that legislation.
   [1913 Webster]

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

KING'S BENCH. The name of the supreme court of law in England. It is so
called because formerly the king used to sit there in person, the style of
the court being still coram ipso rege, before the king himself. During the
reign of a queen, it is called the Queen's Bench, and during the
protectorate of Cromwell, it was called the Upper Bench. It consists of a
chief justices and three other judges, who are, by their office, the
principal coroners and conservators of the peace. 3 Bl. Com. 41.
     2. This court has jurisdiction in criminal matters, in civil causes,
and is a supervisory tribunal to keep other jurisdictions within their
proper bounds.
     3.-1. Its criminal jurisdiction extends over all offenders, and not
only over an capital offences but also over another misdemeanors of a public
nature; it being considered the custos morum of the realm. Its jurisdiction
is so universal that an act of parliament appointing that all crimes of a
certain denomination shall be tried before certain judges, does not exclude
the jurisdiction of this court, without negative words. It may also proceed
on indictments removed into that court out of the inferior courts by
certiorari.
     4.-2. Its civil jurisdiction is against the officers or ministers of
the court entitled to its privilege. 2 Inst. 23; 4 Inst. 71; 2 Bulst. 123.
And against prisoners for trespasses. In these last cases a declaration may
be filed against them in debt, covenant or account: and this is done also
upon the notion of a privilege, because the common pleas could not obtain or
procure the prisoners of the king's bench to appear in their court.
     5.-3. Its supervisory powers extend, 1. To issuing writs of error to
inferior jurisdictions, and affirming or reversing their judgments. 2. To
issuing writs of mandamus to compel inferior officers and courts to perform
the duties required of them by law. Bac. Ab. Court of King's Bench.