What does abamūrus mean in Latin?

abamūrus, a noun, means “a supporting or retaining wall, added to support another wall”.

What is the genitive of abamūrus?

The genitive singular is abamūrī. abamūrus is masculine, second declension.

noun · masculinesecond declension

abamūrus m (genitive abamūrī)

rarea supporting or retaining wall, added to support another wall
Item transpositi sunt abamuri cum Archeriis […]1696, Histoire civile ou consulaire de la ville de Lyon / Glossarium mediae et infimae latinitatis

From mūrus.