[lahy-ter-thuh n-air]
adjective Aeronautics.
  1. (of an aircraft) weighing less than the air it displaces, hence obtaining lift from aerostatic buoyancy.
  2. of or relating to lighter-than-air craft.

Origin of lighter-than-air

First recorded in 1900–05 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for lighter than air

lighter than air

adjective (lighter-than-air when prenominal)
  1. having a lower density than that of air
  2. of or relating to an aircraft, such as a balloon or airship, that depends on buoyancy for support in the air
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012