Acalephae. Class of sea creatures that sting if touched. Includes jellyfish and 'Portuguese man o' war'.
Acamar. Star Eridani. S.H.A. 316°; Dec. S 40°; Mag. 3-1. Acceleration. A hastening or increase in rate of motion. In astronomy, is an apparent gaining of one heavenly body upon another when due to superior speed, a difference of direction, or both of these.
Acceleration of Fixed Stars.Progressive earliness of fixed star transits as compared with Sun's transits. Owing to Sun's eastward movement along Ecliptic, stars transit any meridian nearly four minutes earlier each day when referred to solar time.