底

bottom material; bed material; sludge; sediment; substratum

plantar flexion

Geology

ground moraine

bottom gusset

Anatomy

pelvic floor

Meteorology

cloud base

ownership of leased land where a house is owned by the tenant; rights to real property which is under leasehold

subterranean humanoids (in fiction); mole people

to run out of; to dry up; to be depleted

to hit the bottom; to bottom out

bottomless; unlimited; immeasurable; inexhaustible

depths of Hell

Idiomatic expression

abyss; inescapable situation

do-or-die resistance; resistance to the bitter end

submarine volcano

malicious (at heart); spiteful; wicked

malicious (at heart); spiteful; wicked

making (something) known to everyone; publicizing as widely as possible; dissemination

bottomless; unlimited; immeasurable; inexhaustible

undersea tunnel

undersea cable; submarine cable

to hit the bottom; to bottom out

Jocular, humorous term; Idiomatic expression

thick glasses; bottle bottom glasses

to be found out; to be seen through; to be exposed; to come to light; to be revealed

submarine earthquake

Anatomy

basal ganglia; basal nuclei