The Collaborative International Dictionary of English v.0.48:

Morphology \Mor*phol"o*gy\, n. [Gr. morfh` form + -logy: cf. F.
   morphologie.]
   1. (Biol.) That branch of biology which deals with the
      structure of animals and plants, treating of the forms of
      organs and describing their varieties, homologies, and
      metamorphoses. See Tectology, and Promorphology.
      [1913 Webster]

   2. (Biol.) The form and structure of an organism.
      [PJC]

   3. (Linguistics) The branch of linguistics which studies the
      patterns by which words are formed from other words,
      including inflection, compounding, and derivation.
      [PJC]

   4. Specifically: The study of the patterns of inflection of
      words or word classes in any given language; the study of
      the patterns in which morphemes combine to form words, and
      the rules for combination; morphemics; as, the morphology
      of Spanish verbs; also, the inflection patterns
      themselves.
      [PJC]

WordNet (r) 3.0 (2006):

morphology
    n 1: the branch of biology that deals with the structure of
         animals and plants
    2: studies of the rules for forming admissible words
    3: the admissible arrangement of sounds in words [syn:
       morphology, sound structure, syllable structure, word
       structure]
    4: the branch of geology that studies the characteristics and
       configuration and evolution of rocks and land forms [syn:
       morphology, geomorphology]

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "morphology":
   IC analysis, accidence, affix, affixation, allomorph, anatomist,
   anatomy, angiography, angiology, anthropotomy, bound morpheme,
   bowwow theory, comparative linguistics, conjugation, cutting,
   declension, derivation, descriptive grammar,
   descriptive linguistics, dialectology, difference of form,
   dingdong theory, enclitic, etymology, form, formative, free form,
   generative grammar, geomorphology, glossematics, glossology,
   glottochronology, glottology, grammar, grammatical analysis,
   grammatical theory, grammaticality, graphemics, histologist,
   histology, historical linguistics, immediate constituent analysis,
   infix, infixation, inflection, language study, lexicology,
   lexicostatistics, linguistic geography, linguistic science,
   linguistics, mathematical linguistics, morph, morpheme,
   morphemic analysis, morphemics, morphologist, morphophonemics,
   myography, myology, organography, organology, osteography,
   osteology, paleography, paradigm, parsing, philology, phonetics,
   phonology, phrase-structure grammar, prefix, prefixation,
   proclitic, psycholinguistics, radical, root, rules of language,
   school grammar, semantics, sociolinguistics, splanchnography,
   splanchnology, stem, stratificational grammar, structural grammar,
   structuralism, suffix, suffixation, syntactics, tagmemic analysis,
   tectology, theme, traditional grammar, transformational grammar,
   transformational linguistics, word-formation, zootomy