n.
Pronunciation: ' pr ō -t ō - ˌ pla-n ə t
Function: noun
Date: 1949
: a hypothetical whirling gaseous mass within a giant cloud of gas and dust that rotates around a sun and is believed to give rise to a planet
– pro · to · plan · e · tary \ ˌ pr ō -t ō - ' pla-n ə - ˌ ter- ē \ adjective