The Collaborative International Dictionary of English v.0.48:

Semeiology \Se`mei*ol"o*gy\ (s[=e]`m[-e]*[o^]l"[-o]*j[y^] or
   s[=e]`m[-i]*[o^]l"[-o]*j[y^]), or Semiology \Se`mi*ol"o*gy\
   (s[e^]m`[-e]*[o^]l"[-o]*j[y^]), n. [Gr. shmei^on a mark, a
   sign + -logy.]
   The study of signs as an element of communication; the
   analysis of systems of communication; -- also called
   semiotics. Specifically:
   (a) (Med.) The science of the signs or symptoms of disease;
       symptomatology.
   (b) The art of using signs in signaling.
       [1913 Webster] Semeiotic

The Collaborative International Dictionary of English v.0.48:

Semeiotics \Se`mei*ot"ics\ (s[=e]`m[-i]*[o^]t"[i^]ks), or
Semiotics \Se`mi*ot"ics\, n.
   1. The study of signs as an element of communication; the
      analysis of systems of communication; -- also called
      semiology.
      [PJC]

   2. a theory of signs and symbols, including as branches
      semantics, pragmatics and syntactics. --[RHUD]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Semiography \Se`mi*og"ra*phy\, Semiology \Se`mi*ol"o*gy\,
Semiological \Se`mi*o*log"ic*al\
   Same as Semeiography, Semeiology, Semeiological.
   [1913 Webster]

WordNet (r) 3.0 (2006):

semiology
    n 1: (philosophy) a philosophical theory of the functions of
         signs and symbols [syn: semiotics, semiology]