The Collaborative International Dictionary of English v.0.48:

Runaway \Run"a*way`\, n.
   1. One who, or that which, flees from danger, duty,
      restraint, etc.; a fugitive.
      [1913 Webster]

            Thou runaway, thou coward, art thou fled? --Shak.
      [1913 Webster]

   2. The act of running away, esp. of a horse or teams; as,
      there was a runaway yesterday.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Runaway \Run"a*way`\, a.
   1. Running away; fleeing from danger, duty, restraint, etc.;
      as, runaway soldiers; a runaway horse.
      [1913 Webster]

   2. Accomplished by running away or elopement, or during
      flight; as, a runaway marriage.
      [1913 Webster]
      [1913 Webster]

WordNet (r) 3.0 (2006):

runaway
    adj 1: completely out of control; "runaway inflation"
    n 1: an easy victory [syn: runaway, blowout, romp,
         laugher, shoo-in, walkaway]
    2: someone who flees from an uncongenial situation; "fugitives
       from the sweatshops" [syn: fugitive, runaway, fleer]