from
The Collaborative International Dictionary of English v.0.48
Yardarm \Yard"arm`\, n.
1. (Naut.) Either half of a square-rigged vessel's yard[6],
from the center or mast to the end.
[1913 Webster]
Note: Ships are said to be yardarm and yardarm when so near
as to touch, or interlock yards.
[1913 Webster]
2. (Naut.) The portion of a yard[6] outboard of the slings,
often called the {outer quarter}.
[RDH]
Note: A yard[6] is considered to have four unequal quarters,
two quarters extending from the mast to the slings on
each side, and two smaller outer quarters outboard of
the slings.
[RDH]