WordNet (r) 3.0 (2006):

hang back
    v 1: to lag or linger behind; "But in so many other areas we
         still are dragging" [syn: drag, trail, get behind,
         hang back, drop behind, drop back]

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "hang back":
   avoid, back down, balance, be dilatory, blench, blink, boggle,
   cringe, dawdle, debate, deliberate, demur, dodge, drag, draw back,
   duck, evade, fade, fall back, fall behind, falter, fear,
   fight shy of, filibuster, flinch, gain time, get behind, hang,
   hang fire, hang off, have qualms, hem and haw, hesitate, hold off,
   hover, hum and haw, jib, lag, linger, linger behind, loiter,
   make bones about, make time, pause, play for time, ponder,
   procrastinate, pull back, quail, recoil, reel back, retreat,
   scruple, sheer off, shilly-shally, shrink, shrink back, shy,
   shy at, sidestep, stall, stall for time, stall off, start aside,
   start back, stick at, stickle, stooge around, stop to consider,
   straddle the fence, straggle, strain, strain at, swerve,
   talk against time, temporize, think twice about, trail,
   trail behind, turn aside, waver, weasel, weasel out, wince,
   withdraw, yield