Naval fortification

• The Navy has one in Groton, Connecticut
• The lowest molding of an architectural base or of a baseboard
• U-boat home

Wikipedia Word definitions in Wikipedia
In highway engineering , subbase is the layer of aggregate material laid on the subgrade , on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. ...

WordNet Word definitions in WordNet
n. the lowest molding of an architectural base or of a baseboard

Wiktionary Word definitions in Wiktionary
n. 1 (context architecture English) The lowest projecting part of a baseboard, a pedestal or a similar construct. 2 (context mathematics English) A certain subcollection of a topological space