1.
bottomless; unfathomable; immeasurable
So deep, vast, or extreme that the extent cannot be estimated. Often used figuratively to describe talent, ability, evil, energy, darkness, or other qualities that seem to have no limit.
A fixed expression used prenominally (before a noun) with a literary and somewhat dramatic nuance. Literally "bottom-unknowable," it combines 底 (bottom) + 知れない (cannot be known). Grammatically it behaves like a fixed modifying phrase rather than a regular i-adjective — you almost always see it followed directly by a noun, not used as a predicate ending in だ.
Common collocations
- 底知れない力: unfathomable power
- 底知れない才能: unfathomable talent
- 底知れない闇: unfathomable darkness
- 底知れない恐怖: unfathomable fear
- 底知れない魅力: unfathomable charm
- 底知れない不安: bottomless unease
Similar words
- 計り知れない: immeasurable — very close in meaning, but more common and neutral; can describe damage, value, kindness, influence, etc.
- 果てしない: endless — emphasizes spatial or temporal boundlessness (the horizon, a journey, dreams)
- 限りない: boundless, limitless — similar but more positive, often used with love, possibilities, joy
Usage
底知れない suggests mystery and depth — something whose extent is hidden or concealed, not just large. It is more literary than its close synonym 計り知れない and is often found in novels, essays, and dramatic writing. It is rarely used as a predicate; native speakers say 底知れない力がある rather than その力は底知れない.