The Collaborative International Dictionary of English v.0.48:
Phenomenon \Phe*nom"e*non\, n.; pl. Phenomena. [L.
phaenomenon, Gr. faino`menon, fr. fai`nesqai to appear,
fai`nein to show. See Phantom.]
1. An appearance; anything visible; whatever, in matter or
spirit, is apparent to, or is apprehended by, observation;
as, the phenomena of heat, light, or electricity;
phenomena of imagination or memory.
In the phenomena of the material world, and in many
of the phenomena of mind. --Stewart.
2. That which strikes one as strange, unusual, or
unaccountable; an extraordinary or very remarkable person,
thing, or occurrence; as, a musical phenomenon.