D defs.my
Entry 3 senses Webster, 1913

effusive

/ĕf'-yo͞os-ĭv/ · ef·fu·sive · IPA /ɪˈfjuːsɪv/
01 a. Pouring out; pouring forth freely.
  1. 1.
    Pouring out; pouring forth freely.[archaic]
  2. 2.
    formed by an outpouring of molten lava, or pertaining to rocks so formed.(Geol.)
  3. 3.
    overly demonstrative; expressing emotion in an unrestrained manner; exhibiting unrestrained enthusiasm; -- of people and human actions; as, effusive thanks; an effusive letter of recommendation. Contrasted with reserved.
Phrases & compounds
Effusive rocks — volcanic rocks formed by a nonexplosive outpouring of lava in molten or plastic form; in distinction from so-called intrusive, or plutonic, rocks.