The group of persons selected to hear the evidence in a trial and render a verdict on matters of fact. See also grand jury.

Source: U.S. Courts

A group of citizens picked according to law and authorized to decide a case. Can be: (1) grand, that is, a body of citizens that determines whether probable cause exists that a crime has been committed and whether an indictment should be issued; (2) hung, that is, a jury that can't agree on a verdict after a suitable period of deliberation; (3) petit (or "trial"), that is, an ordinary jury for the trial of a criminal or civil action; or (4) special, that is, a jury ordered by the court, on the motion of either side, in cases that are unusually important or complicated. (See also grand jury, petit jury.)

Source: California Courts.