noun
flying saucer
Refers to a disc-shaped unidentified flying object, often associated with science fiction and UFO sightings.
夜空に空飛ぶ円盤のような光を見た。
I saw a light like a flying saucer in the night sky.
UFO is a broader term for any unidentified flying object, while 空飛ぶ円盤 specifically describes the classic disc-shaped craft.
Compound of 空 (sora, 'sky'), 飛ぶ (tobu, 'to fly'), and 円盤 (enban, 'disc'). A calque of English 'flying saucer'.