Dip, to

To lower, normally the ensign or national flag, as a sign of courtesy, and especially when passing one of the Queen’s ships. The ensign is lowered about half down its staff as you draw level with the ship, which should dip in return. After she has dipped you return your ensign to its normal height. (Many small cruisers have such a short staff that the proper procedure cannot be followed: in such cases it is normal to remove the staff from its socket and tilt it down to a roughly horizontal position.)