bottomless; unfathomable; immeasurable
Describes something so deep or vast that its limits cannot be perceived, often used figuratively for potential, power, or depth of feeling. Related to the literary form 底知れぬ.
See also: 底知れぬ
His talent is bottomless; there's no telling how far he'll go.
The lake is said to be of unfathomable depth.
Compound of 底 (そこ, 'bottom') + 知れず (しれず, the negative continuative form of 知れる, 'to be known'). Literally 'without the bottom being known'.