noun
hypnagogic hallucination
Medical term for vivid sensory experiences that occur while falling asleep.
入眠時幻覚は、眠りに入る直前に現れる幻覚です。
Hypnagogic hallucinations are hallucinations that appear just before falling asleep.
Compound of 入眠 (にゅうみん, 'falling asleep'), 時 (じ, 'time'), and 幻覚 (げんかく, 'hallucination').