Comet and Extraterrestrial object

Comet noun - (astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit.

Extraterrestrial object and comet are semantically related. In some cases you can use "Extraterrestrial object" instead a noun "Comet".

Extraterrestrial object noun - A natural object existing outside the earth and outside the earth's atmosphere.

Comet and extraterrestrial object are semantically related. Sometimes you can replace term "Comet" with "Extraterrestrial object", this terms are similar.