Trailing A term used to describe the most recent time period. Investopedia Says: Most often you will hear the term "trailing 12 months", and, from time to time, "trailing three months" or "trailing six months". The term may also modify a reported metric. For example, the earnings in a trailing price-to-earnings ratio refers to the past earnings per share over a certain period - usually 12 months. Trailing 12 months is denoted by the acronym "TTM". Related Terms: Cash Earnings Per Share - Cash EPS Diluted Earnings Per Share - Diluted EPS Earnings Earnings per Share - EPS Price-Earnings Ratio - P/E Ratio Trailing Twelve Months - TTM |