n. [ Gr. &unr_;; &unr_; = &unr_; twice + ga`mma the letter Γ. So called because it resembled two gammas placed one above the other. ] (Gr. Gram.) A letter (&unr_;, &unr_;) of the Greek alphabet, which early fell into disuse. [ 1913 Webster ]

☞ This form identifies it with the Latin F, though in sound it is said to have been nearer V. It was pronounced, probably, much like the English W.

{ } a. Having the digamma or its representative letter or sound; as, the Latin word vis is a digammated form of the Greek 'i`s. Andrews. [ 1913 Webster ]

n. The third letter (Γ, γ = Eng. G) of the Greek alphabet. [ 1913 Webster ]

n. A cross formed of four capital gammas, formerly used as a mysterious ornament on ecclesiastical vestments, etc. See Fylfot. [ 1913 Webster ]

. n. (Physics) A very penetrating electromagnetic ray not appreciably deflected by a magnetic or electric field, emitted by radioactive substances. Gamma rays are photons of electromagnetic radiation having a wavelength shorter than that of X-rays, (i. e. shorter than 0.1 nanometer) and are correspondingly more penetrating than X-rays. In addition to being given off in certain types of radioactive decay, they may be found in cosmic radiation, though they are largely absorbed by the earth's atmosphere. Gamma-ray detectors orbited above the atmosphere have found bursts of gamma radiation, in some cases associated with visually observed supernova explosions, but in most cases from unidentified sources. [ Webster 1913 Suppl. +PJC ]