From The Collaborative International Dictionary of English v.0.48 [gcide]:
Ferryboat \Fer"ry*boat`\, n.
A vessel for conveying passengers, merchandise, etc., usually
across streams, rivers, bays, and other narrow waters.
Syn: ferry[2].
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
ferryboat
n 1: a boat that transports people or vehicles across a body of
water and operates on a regular schedule [syn: ferry,
ferryboat]