Source : Webster's Revised Unabridged Dictionary (1913)

Swear \Swear\, v. t.
   1. To utter or affirm with a solemn appeal to God for the
      truth of the declaration; to make (a promise, threat, or
      resolve) under oath.

            Swear unto me here by God, that thou wilt not deal
            falsely with me.                      --Gen. xxi.
                                                  23.

            He swore consent to your succession.  --Shak.

   2. (Law) To put to an oath; to cause to take an oath; to
      administer an oath to; -- ofetn followed by in or into;
      as, to swear witnesses; to swear a jury; to swear in an
      officer; he was sworn into office.

   3. To declare or charge upon oath; as, he swore treason
      against his friend. --Johnson.

   4. To appeal to by an oath.

            Now, by Apollo, king, Thou swear'st thy gods in
            vain.                                 --Shak.

   {To swear the peace against one}, to make oath that one is
      under the actual fear of death or bodily harm from the
      person, in which case the person must find sureties that
      he will keep the peace.