WordNet (r) 3.0 (2006):

drift away
    v 1: lose personal contact over time; "The two women, who had
         been roommates in college, drifted apart after they got
         married" [syn: drift apart, drift away]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "drift away":
   decline, die away, diminish, dwindle, ebb, fade, fade away, go,
   go away, move away, move off, pull away, recede, retire, retreat,
   retrocede, shrink, sink, stand off, wane, widen the distance,
   withdraw