(1) Solid rock underlying the various soil layers.
(2) Any solid rock exposed at the earth's surface or covered by unconsolidated or loose material.
(3) Solid rock material underlying soils and other earthy rock formations. Bedrock is sometimes exposed when topsoil is eroded or cut away.
(1) We hiked on bedrock, which you can't do that often. The nice thing, if there is one, is that it never wears out because it's bedrock all the way down.
(2) Bedrock - it's called that because it never moves. It only lies there, under everything else, snoring deeply.
(3) At the bottom of everything else, you get bedrock.