Mariana Trench (deepest part of the ocean, near the Mariana Islands)
multipurpose underground utility conduit
Marco Polo Bridge Incident (July 7, 1937)
Marco Polo Bridge (China)
sulcus; groove in the surface of the brain
nasolabial sulcus; nasolabial groove; nasolabial fold
gutter oil; recycled waste oil sold illicitly in China as a cheaper alternative to cooking oil
drain and pool for collecting sewage, etc.
lateral sulcus (brain structure); Sylvian fissure; lateral fissure
subterranean drain; culvert; conduit
L-shaped gutter; L-shaped drain
Solenogastres (subclass of small worm-like molluscs)
epidermal depression; skin depression