weightless

from WordNet (r) 3.0 (2006)

weightless
    adj 1: having little or no weight or apparent gravitational
           pull; light; "floating freely in a weightless condition";
           "a baby bat...fluffy and weightless as a moth"; "jackets
           made of a weightless polyester fabric" [ant: {weighty}]

from The Collaborative International Dictionary of English v.0.48

Weightless \Weight"less\, a.
   Having no weight; imponderable; hence, light. --Shak.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

33 Moby Thesaurus words for "weightless":
      airy, bodiless, bubbly, downy, ethereal, featherweight, feathery,
      fluffy, foamy, frothy, gossamery, immaterial, impalpable,
      imponderable, imponderous, incorporeal, insubstantial, intangible,
      leger, light, light as air, lighter than vanity, lightweight,
      mousse, nonsubstantial, souffle, unconcrete, unheavy, unsolid,
      unsubstanced, unsubstantial, volatile, yeasty

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