A market driven by forces that could be in place for many years, causing the price of a particular investment or asset class to rise or fall over a long period of time. In a secular bull market, strong investor sentiment drives prices higher, as there are more net buyers than sellers. In a secular bear market, weak sentiment causes selling pressure over an extended period of time.
Taobiz explains Secular Market
Secular markets are typically driven by large-scale national and worldwide events, which occur in combination. For example, wars, demographic/population shifts and governmental/political policies are all events that could drive secular markets.
A secular bull market will have bear market periods within it, but it will not reverse the overlying trend of upward asset values. For example, most economists agree that U.S. equities were in a secular bull market from about 1980 to 2000, even though the stock market crash of 1987 occurred within the same time period. The losses from that bear market period were quickly recovered, and the market indexes continued to rise over the next 13 years. The Standard & Poor's 500 Index rose from 120 to nearly 1,500 during this secular bull market.