The Collaborative International Dictionary of English v.0.48:

Straggler \Strag"gler\, n.
   1. One who straggles, or departs from the direct or proper
      course, or from the company to which he belongs; one who
      falls behind the rest; one who rambles without any settled
      direction.
      [1913 Webster]

   2. A roving vagabond. --Shak.
      [1913 Webster]

   3. Something that shoots, or spreads out, beyond the rest, or
      too far; an exuberant growth.
      [1913 Webster]

            Let thy hand supply the pruning knife,
            And crop luxuriant stragglers.        --Dryden.
      [1913 Webster]

   4. Something that stands alone or by itself.
      [1913 Webster]

WordNet (r) 3.0 (2006):

straggler
    n 1: someone who strays or falls behind [syn: straggler,
         strayer]