Pronunciation: (bā'tuor, esp. Brit., bē'-),[key] —n. 1. the second letter of the Greek alphabet (β, B).
2. the consonant sound represented by this letter.
3. (cap.) Astron.a star that is usually the second brightest of a constellation: The second brightest star in Taurus is Beta Tauri. 4. Chem. a. one of the possible positions of an atom or group in a compound.
b. one of two or more isomeric compounds.
5. the second of any series, as in chemistry or physics.
6. Also called beta coefficient, beta line.Stock Exchange.an arbitrary measure of the volatility of a given stock using an index of the volatility of the market as a whole: A beta of 1.1 indicates a stock that is 10 percent more volatile than the market. 7. (cap.) Trademark.a brand of tape format for VCR tape, incompatible with other formats. Cf. VHS. 8. Chiefly Brit.a grade showing that a student is in the middle or second of three scholastic sections in a class. Cf. alpha (def. 7), gamma (def. 9).