1) Bottom 2) Lower side 3) The lower abdomen 4) Undersurface 5) Vulnerable area 6) Vulnerable part 1) Underbody 
[venue] The Underbelly is a venue at the Edinburgh Festival Fringe off Cowgate. From 2001-2004, Underbelly was the only venue operated by Underbelly Limited. In 2005, Underbelly added the Baby Belly venue. In 2006, these venues were joined by the E4 UdderBELLY and the Cow Barn. ==History of the Underbelly== Underbelly was first opened in 20...
[n] - lower side 2. [n] - the soft belly or underside of an animal`s body 3. [n] - the quality of being weak or unprotected
underbody noun the soft belly or underside of an animal`s body
The RV's underfloor surface, which is protected by a weatherproofed material.
the lower abdomen; posterior ventral area, as of an animal's body. · the lower surface of an object; underside: the underbelly of an airplane. · a vulnerable area; weak point: an attack on the soft underbelly of Europe. · a dark, seamy, often hidden area or side: a police officer continually exposed to the underbelly of society.