tackle consisting of a single and a double block for use with rope having a large diameter
—vb
3.
nautical to head (a sailing vessel) into the wind so that her sails flap
4.
(intr) nautical (of a sail) to flap when the wind is blowing equally on both sides
5.
to move the jib of (a crane) or raise or lower the boom of (a derrick) in order to shift a load
[C13 (in the sense: steering gear): from Old French lof, perhaps from Middle Dutch loef peg of a tiller; compare Old High German laffa palm of hand, oar blade, Russian lapa paw]