From The Collaborative International Dictionary of English v.0.48 :
Steerer \Steer"er\ (-[~e]r), n.
One who steers; as, a boat steerer.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
steerer
n 1: the person who steers a ship [syn: helmsman, steersman,
steerer]
2: a beguiler who leads someone into danger (usually as part of
a plot) [syn: decoy, steerer]