Real Dictionary

derrick
countable noun: A derrick is a machine that is used to move cargo on a ship by lifting it in the air.
countable noun: A derrick is a tower built over an oil well which is used to raise and lower the drill.

derrick in American English
a large apparatus for lifting and moving heavy objects: it consists of a long beam pivoted at the base of a vertical, stationary beam and moved by ropes running on pulleys
luff
noun: a jib crane having a boom hinged near the base of the mast so as to rotate about the mast, for moving a load toward or away from the mast by raising or lowering the boom

derrick in British English
noun: a simple crane having lifting tackle slung from a boom
verb: to raise or lower the jib of (a crane)

derrick in the Oil and Gas Industry
noun: A derrick is the structure over an oil well which supports the drilling equipment and allows it to be lifted into and out of the wellbore.