unusual space; other dimension
Refers to a space that feels separate from normal reality, often used in science fiction, fantasy, or to describe a surreal atmosphere.
This room feels like an otherworldly space.
The protagonist of the story wandered into a different dimension.
Compound of 異 (い, 'different') + 空間 (くうかん, 'space'). The exact origin is uncertain, but it follows a common pattern for creating terms describing alternate or unusual spaces.