marked by the expression of great or excessive emotion or enthusiasm
archaic : pouring freely
characterized or formed by a nonexplosive outpouring of lava
Lila’s history teacher wrote an effusive letter of recommendation.
“It’s never easy for opponents from the opposite party to find specific praise at library unveilings, but Carter was effusive. ‘Mr. President, let me say that I’m filled with admiration for you and deep gratitude for you about the great contributions you’ve made to the most needy people on Earth,’ said the 39th president.” — From an article by John Dickerson on Slate.com, July 2, 2013.
We’ve used “effusive” in English to describe excessive outpourings since the 17th century. In the 1800s, geologists adopted the specific sense related to flowing lava—or to hardened rock formed from flowing lava. “Effusive” can be traced to the Latin verb “effundere” (“to pour out”), which itself comes from “fundere” (“to pour”) plus a modification of the prefix “ex-” (“out”). Our verb “effuse” has the same Latin ancestors. A person effuses when he or she speaks effusively. Liquids can effuse as well (as in “water effusing from a pipe”).