| Noun | 1. | interplanetary gas - a rarefied flow of gas and charged particles (plasma) that stream from the sun and form the solar wind interplanetary medium - interplanetary space including forms of energy and gas and dust solar wind - a stream of protons moving radially from the sun plasma - (physical chemistry) a fourth state of matter distinct from solid or liquid or gas and present in stars and fusion reactors; a gas becomes a plasma when it is heated until the atoms lose all their electrons, leaving a highly electrified collection of nuclei and free electrons; "particles in space exist in the form of a plasma" |