A rocket engine, especially a solid rocket or a hybrid rocket.

A reaction engine that obtains thrust by jet propulsion which forms its jet exclusively from propellant.

The sport of scaling rock faces, either with or without ropes and other equipment.

(uncountable) Rock that is carved in situ. / Any of various dwarf succulent plants that resemble stones. / Pyura chilensis, a tunicate that resembles a mass of organs inside a rock.

The science that studies the mechanical behaviour of rock.

(idiomatic) In a difficult and inescapable position. / (idiomatic) Having the choice between two unpleasant or distasteful options; in a predicament or quandary.

(UK) A private road, where the local borough council is not responsible for the road's maintenance.

(dated) naphtha

(anatomy) Any of the cylindrical photoreceptor cells in the retina that function in dim light levels.

(music) A musical genre combining elements of pop music and rock music.