in·creas·er \-sə(r)\noun (-s) : one that increases: as a.: an agent that causes something to increase < these increasers of public turmoil > b.archaic: one that promotes or furthers something (as a cause, a group) c.: a plant or animal that tends to multiply freely < several of the new glads proved to be excellent increasers > d.: a coupling for joining a pipe to another of larger diameter