The embryo of a seed, especially of a seed used as a cereal or grain. See Wikipedia article on cereal germ.

The total capacity of boats, as of lifeboats on a ship. / Conveyance by boat. / A charge for transporting goods by boat.

A laser that operates by analogy with an electronic waterfall, with electrons cascading down a series of small steps emitting a photon at each step.

Idiomatic.