1 the second letter of the Greek alphabet (B, szlig).
2 a second-class mark given for a piece of work or in an examination.
3 Astron. the second brightest star in a constellation.
4 the second member of a series.
Phrases and idioms:
beta-blocker Pharm. a drug that prevents the stimulation of increased cardiac action, used to treat angina and reduce high blood pressure. beta particle (or ray) a fast-moving electron emitted by radioactive decay of substances (orig. regarded as rays).
Etymology: ME f. L f. Gk
Useful english dictionary. 2012.