Merriam-Webster's Collegiate® Dictionary, 11th Edition
JETTY
I. noun (plural jetties) see: jet
Date: 15th century
1. a structure extended into a sea, lake, or river to influence the current or tide or to protect a harbor, a protecting frame of a pier, a landing wharf,
II. intransitive verb (jettied; jettying)
Date: 1598
project , jut ,
III. adjective
Date: 1586
black as jet