Oarlock n. : The notch, fork, or other device on the gunwale of a boat, in which the oar rests in rowing. See Rowlock.

Example:
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Taxonomy
rowlock, oar, free encyclopedia, rowing boat, pin, oarlock, search, attaches, acts, propulsive force, rower, thrust, craft, riggers, project, leverage, sport rowing, U-shaped.

Defination from the web:
oarlock (US) is a brace that attaches an oar to a boat. ... When a boat is rowed, the rowlock acts as a fulcrum, and, in doing so, the propulsive force that the rower exerts on ...