Effusive \Ef*fu"sive\, a. Pouring out; pouring forth freely. ``Washed with the effusive wave.'' --Pope.

Effusive rocks (Geol.), volcanic rocks, in distinction from so-called intrusive, or plutonic, rocks. -- Ef*fu"sive*ly, adv. -- Ef*fu"sive*ness, n.

Source: Webster's Revised Unabridged Dictionary (1913)