a : occurring once in an age or a century b : existing or continuing through ages or centuries c : of or relating to a long term of indefinite duration

https://www.merriam-webster.com/dictionary/secular

https://www.nytimes.com/1996/03/24/business/market-watch-oil-spurt-a-rally-that-few-believe.html "Sure, there can be market hiccups, but the secular trend is against rising prices of real things and for rising prices of stocks and bonds."

https://www.washingtonpost.com/opinions/us-risks-falling-off-a-global-cliff/2012/10/25/38cdc85c-1ebe-11e2-9cd5-b55c38388962_story.html "If so, a long-term secular trend of higher interest rates, a lower dollar and stunted GDP growth would contaminate an already polluted fiscal chemistry lab with a fiscal gap of growing and unacceptably large proportions."

https://www.huffpost.com/entry/the-recession-is-over-but_b_375770 "The secular force is the D-process and the deleveraging, so I expect deflation to be the resulting secular trend more than inflation."

https://www.cnn.com/2020/01/18/health/13-reasons-why-study-suicides-trnd/index.html "I take issue with their analysis which did not take into account the secular trend in suicide and the large increase that occurred in 2017 in young men."

The word "secular" has been used in this manner referring to things over a much longer term in multiple Fields including investment, astronomy, medicine, sociology, climate. It's in the dictionary. Its Used in major newspapers. When I used the term originally referring to secular cycles specifically, I immediately followed the use of the term with a general explanation of what I meant, it was the next sentence in the same paragraph.