lubricant

A substance, such as grease or oil, that reduces friction when applied as a surface coating to moving parts.

A slippery liquid, gel, or oil that is used to reduce friction on or soreness of body tissue.

One that facilitates conversation or cooperation.

Lubricating.

Any natural or artificial material that may be used to lubricate the rubbing surfaces of machinery, in order to lessen their friction upon each other.