(nonce word) A word of disputed meaning; perhaps, abounding in marsh marigolds.

(physics) Any of three semistable mesons, having positive, negative or neutral charge, composed of up and down quarks/antiquarks.

plural of pion

(physics, of a theory) That includes pions

A theoretical type of antimatter rocket which uses proton-antiproton fuel, and magnetic rocket funnels to direct the π-on exhaust. The pi meson particles are created by the matter-antimatter annihilation of protons and antiprotons.

plural of pion rocket

In a pioneering manner

(neurology) An axon that lays down the initial growing path for the other axons of the same neuron to follow.

(transitive) To be the first to do or achieve (something), preparing the way for others to follow.

One who goes before, as into the wilderness, preparing the way for others to follow. / A person or other entity who is first or among the earliest in any field of inquiry, enterprise, or progress.