Seconder

n.

1.

One who seconds{3} or supports what another attempts, affirms, moves, or proposes; as, the seconder of an enterprise or of a motion.

Noun

1.

seconder - someone who endorses a motion or petition as a necessary preliminary to a discussion or vote

Maecenas, abettor, admirer, advocate, aficionado, angel, apologist, backer, buff, champion, defender, dependence, encourager, endorser, exponent, fan, favorer, friend at court, lover, mainstay, maintainer, paranymph, partisan, patron, promoter, protagonist, reliance, second, sectary, sider, sponsor, stalwart, standby, support, supporter, sustainer, sympathizer, upholder, votary, well-wisher