Pronunciation: (gam'u),[key] —n. 1. the third letter of the Greek alphabet (Γ, γ).
2. the consonant sound represented by this letter.
3. the third in a series of items.
4. (cap.) Astron.a star that is usually the third brightest of a constellation: The third brightest star in the Southern Cross is Gamma Crucis. 5. a unit of weight equal to one microgram.
6. Physics.a unit of magnetic field strength, equal to 10-5 gauss.
7. Photog.a measure of the degree of development of a negative or print.
8. Television.an analogous numerical indication of the degree of contrast between light and dark in the reproduction of an image in television.
9. Chiefly Brit.a grade showing that an individual student is in the third, or lowest, of three scholastic sections in a class. Cf. alpha (def. 7), beta (def. 8).