Definition of "afterguard"

There were times when the whole crew refused their duty; and we of the afterguard were twice got under arms—being the first time that ever I bore weapons—in the fear of mutiny.

1889, Robert Louis Stevenson, chapter IX, in The Master of Ballantrae, Cassell

Yet from something in the outline and carriage, Billy took him to be, and correctly, one of the afterguard.

1924, Herman Melville, chapter 12, in Billy Budd‎, London: Constable & Co.

This is his sixth Cup campaign but his first as skipper, a position he inherited after the helmsman Russell Coutts, Butterworth’s longtime alter ego in the afterguard, bolted from Alinghi in 2004.

2007 July 3, Christopher Clarey, “A Familiar Foe Blocks New Zealand’s Path”, in New York Times‎