oceanic trench; deep-sea trench; deep
Mariana Trench (deepest part of the ocean, near the Mariana Islands)
multipurpose underground utility conduit
Marco Polo Bridge Incident (July 7, 1937)
ligature mark; constriction mark; strangulation groove
Marco Polo Bridge (China)
sulcus; groove in the surface of the brain
nasolabial sulcus; nasolabial groove; nasolabial fold
Liutiaohu Incident (1931 railway bombing triggering the Manchurian Incident)
gutter oil; recycled waste oil sold illicitly in China as a cheaper alternative to normal cooking oil
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)
drain and pool for collecting sewage, etc.
mammary slit (in whales, dolphins and porpoises); cleavage (between breasts)
epidermal depression; skin depression