We don't have synonyms for aggers yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are daggers, agger and angers.
(n) :
(historical) Synonym of earthwork in ancient Roman contexts, particularly a defensive wall or mound.
(n) :
A double tide, particularly a high tide in which the water rises to a given level, recedes, and then rises again (or only the second of these high waters), but sometimes equally a low tide in which the water recedes to a given level, rises, and then recedes again
(n) :
(historical) Synonym of earthwork in ancient Roman contexts, particularly a defensive wall or mound.
(n) :
A double tide, particularly a high tide in which the water rises to a given level, recedes, and then rises again (or only the second of these high waters), but sometimes equally a low tide in which the water recedes to a given level, rises, and then recedes again