Bottomless, unfathomable. literal and figurative. Obsolete.

That has no bottom. Sometimes in figurative contexts.

That has great downward or inward extent; very deep.

Nautical. Of water: deep; esp. deep close to the shore. Also in neal to. Cf. nealed to at nealed, adj.2

Of water, the sea, etc.: That cannot be sounded; unfathomable. Frequently figurative or in figurative context.

Incapable of being sounded; unfathomable.

figurative. Deep as an abyss; abysmal. Obsolete.

Having no bottom; bottomless. Also figurative.

Of which the depth cannot be sounded; fathomless; abyssal.

Incapable of being sounded; unfathomable.

so deep as to reach the chin; figurative very deep, deeply immersed in.

That cannot be measured with a fathom line; of measureless depth. Often of a metaphorical ‘abyss’.

Having no foundation or basis; chiefly figurative, groundless, unwarranted.

Of, relating to, or resembling an abyss; bottomless; profound; spec.: of, resembling, or relating to Hell; hellish.

That cannot be plumbed; immeasurably deep; bottomless. Also figurative.

Incapable of being fathomed or measured; unsoundable, immeasurable, vast. Of space (esp. in depth).

Of the nature of or like a chasm.

= fathoms deep at sense 3d, excessively deep.

unfathomable.

Of the nature of or belonging to a chasm.

Characteristic of an abyss; unfathomable.