D defs.my
Entry 1 sense Webster, 1913

Ultragaseous

· Ul·tra·gas·e·ous · IPA
01 a. Having the properties exhibited by gases under very low pressures (one millionth of an atmosphere or less). Matter under this condition, wh…
  1. 1.
    Having the properties exhibited by gases under very low pressures (one millionth of an atmosphere or less). Matter under this condition, which has been termed the fourth state of matter, is sometimes called radiant matter.(Physics)