tiny; very small; postage-stamp-sized
Idiomatic expression literally meaning 'like a cat's forehead'; used to describe a very small space, especially a room, apartment, or garden. Often used humorously or self-deprecatingly.
My room is as small as a cat's forehead.
It's a tiny garden, but I enjoy planting flowers in it.
Literally 'like a cat's forehead'. The phrase plays on the small size of a cat's forehead to humorously describe a tiny space. The exact origin is uncertain, but it is a well-established idiomatic simile in modern Japanese.