Merriam-Webster Collegiate Dictionary - audible

 I. adjective  Etymology: Late Latin audibilis, from Latin audire to hear; akin to Greek aisthanesthai to perceive, Sanskrit avis evidently  Date: 1529 heard or capable of being heard  • audibility noun  • audibly adverb  II. noun  Date: 1962 a substitute offensive or defensive play called at the line of scrimmage in football  III. intransitive verb  (-bled; audibling)  Date: 1974 to call an ~ ~d to a pass play — Peter King