| a measure of the effectiveness of a pitcher, obtained by dividing the number of earned runs scored against the pitcher by the number of innings pitched and multiplying the result by nine. A pitcher yielding three earned runs in nine innings has an earned run average of 3.00. Abbreviation: ERA, era |
| earned run average n. Baseball Abbr. ERA A measure of a pitcher's performance obtained by dividing the total of earned runs allowed by the total of innings pitched and multiplying by nine. |