adjective (a)

• having little or no weight or apparent gravitational pull; light(adj.all)

  Example:
  Floating freely in a weightless condition.
  A baby bat...fluffy and weightless as a moth.
  Jackets made of a weightless polyester fabric.
  

  Antonym:
  weighty
  

  source: wordnet30
• Having no weight; imponderable; hence, light.(adjective)

  source: webster1913