By Mayo Clinic Staff. Erectile dysfunction â the inability to get and keep an erection firm enough for sex â is a common problem. You've likely seen advertisements for erectile dysfunction herbs or supplements to increase your sexual performance..
plate tectonics. In geology, a theory that the Earth's lithosphere (crust and upper mantle) is divided into a number of large, plate-like sections that move as distinct masses. See Notes at fault, Gondwanaland, See more at tectonic boundary.
Definition of trench - a long, narrow ditch, a long, narrow, deep depression in the ocean bed, typically one running parallel to a plate boundary and mar Definition of trench - a long, narrow ditch, a long, narrow, deep depression in the ocean bed, typically one running parallel to a plate boundary and mar