The Collaborative International Dictionary of English v.0.48:
Steerageway \Steer"age*way`\ (-w[=a]`), n. (Naut.) A rate of motion through the water sufficient to render a vessel governable by the helm. [1913 Webster]WordNet (r) 3.0 (2006):
steerageway n 1: (nautical) the minimum rate of motion needed for a vessel to be maneuvered