In the act or state of grinning; on the grin: as, “his visage all agrin,”

adverb. In the act of grinning.

adjective. grinning; having happiness or satisfaction apparent on one's face

noun. a protein involved in the formation of neuromuscular junctions during embryonic development

"When axon terminals touch the ephrin-A5-expressing postsynaptic region, EphA4 associated with Meltrin β is localized preferentially at the axon terminal opposite the postsynaptic cluster on the muscle fiber; Meltrin β interferes with the internalization of the ephrin-A5-EphA4 complexes so that the axon terminal and muscle could avoid receiving a repulsive signal at the NMJ, and many molecules, such as agrin, MuSK and adhesion proteins, cooperate in stabilization of the NMJ."