A hydrospring or hydro-spring is a spring damped by hydraulic fluid (typically oil) being driven through holes in a piston, as the piston moves in response to a force.
The spring is often made of rubber.
Inside a rubber hydrospring there are hydraulic viscous damping systems which damp movement in all three directions but require very few parts.
Even the slack adjustment may be integrated into the element.
[1] Hydrosprings are used mainly as shock absorbers in applications such as damped suspension in railway bogies, bulldozer blade shock absorbers and as recoil absorbers for artillery.