The Collaborative International Dictionary of English v.0.48:

Drift \Drift\, v. i. [imp. & p. p. Drifted; p. pr. & vb. n.
   Drifting.]
   1. To float or be driven along by, or as by, a current of
      water or air; as, the ship drifted astern; a raft drifted
      ashore; the balloon drifts slowly east.
      [1913 Webster]

            We drifted o'er the harbor bar.       -- Coleridge.
      [1913 Webster]

   2. To accumulate in heaps by the force of wind; to be driven
      into heaps; as, snow or sand drifts.
      [1913 Webster]

   3. (mining) to make a drift; to examine a vein or ledge for
      the purpose of ascertaining the presence of metals or
      ores; to follow a vein; to prospect. [U.S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

drifting
    adj 1: continually changing especially as from one abode or
           occupation to another; "a drifting double-dealer"; "the
           floating population"; "vagrant hippies of the sixties"
           [syn: aimless, drifting, floating, vagabond,
           vagrant]
    n 1: aimless wandering from place to place

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "drifting":
   ascending, axial, back, back-flowing, backward, circumforaneous,
   descending, discursive, divagatory, down-trending, downward,
   errant, flitting, floating, flowing, fluent, flying, footloose,
   footloose and fancy-free, fugitive, gadding, going, gypsy-like,
   gypsyish, gyrational, gyratory, landloping, meandering,
   migrational, migratory, mounting, nomad, nomadic, passing,
   plunging, progressive, rambling, ranging, reflowing, refluent,
   regressive, retrogressive, rising, roaming, rotary, rotational,
   rotatory, roving, running, rushing, shifting, sideward, sinking,
   soaring, straggling, straying, streaming, strolling, traipsing,
   transient, transitory, transmigratory, up-trending, upward,
   vagabond, vagrant, wandering