plural of Devonian

A female mediator; a mediatrix.

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.

(ichthyology) Of a fish's tail, such that the vertebral column bends and extends upwards into the upper lobe of the tail, making it larger than the lower lobe; as in sharks, rays, and skates.