n. 俯仰运动(上下摆动,起重杆的升降)

Luff \Luff\ (l[u^]f), v. i. [imp. & p. p. {Luffed} (l[u^]ft); p.
pr. & vb. n. {Luffing}.]
1. (Naut.) To turn the head of a vessel toward the wind; to
sail nearer the wind; to turn the tiller so as to make the
vessel sail nearer the wind.

2. (Naut.) To flutter or shake from being aligned close to
the direction of the wind; -- said of a sail.
[PJC]

{To luff round}, or {To luff alee}, to make the extreme of
this movement, for the purpose of throwing the ship's head
into the wind.