Meniscus was the personal Imperial-class Star Destroyer of Grand Admiral Martio Batch. The executive officer of the Meniscus betrayed and executed Batch following the Battle of Endor, and joined Admiral Blitzer Harrsk in the Deep Core.
Behind the scenes
Dan Wallace originally named the Meniscus in a segment of his Grand Admirals article that was cut, and is therefore unofficial. All other information on it is official.
A meniscus is a type of lens; the ship was given the name due to Batch's involvement with cloaking research.
Sources
"Who's Who: Imperial Grand Admirals" — Star Wars Insider 66 (First mentioned) (Cut content)
Grand Admirals: What Have They Got in their Pocketsses? on Continuity, Criticisms, and Captain Panaka — Daniel Wallace's StarWars.com Blog (original site is defunct)