Noun
こうくうぼかん
その航空母艦は突然視界から消えたんです。
The aircraft carrier suddenly disappeared out my field of vision.
An aviation (航空) mother warship is a warship that is like mother to all the aviation things (the airplanes). They come home to their mother warship, which is an aircraft carrier.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.