The Collaborative International Dictionary of English v.0.48:

Morphologic \Mor`pho*log"ic\, Morphological \Mor`pho*log"ic*al\,
   a. [Cf. F. morphologique.] (Biol.)
   Of, pertaining to, or according to, the principles of
   morphology. -- Mor`pho*log"ic*al*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

morphological
    adj 1: relating to or concerned with the formation of admissible
           words in a language [syn: morphologic, morphological]
    2: pertaining to geological structure; "geomorphological
       features of the Black Hills"; "morphological features of
       granite"; "structural effects of folding and faulting of the
       earth's surface" [syn: geomorphologic, geomorphological,
       morphologic, morphological, structural]
    3: relating to or concerned with the morphology of plants and
       animals; "morphological differences" [syn: morphologic,
       morphological, structural]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "morphological":
   affixal, anatomic, architectonic, architectural, constructional,
   derivational, descriptive, edificial, formal, glottochronological,
   grammatic, graphemic, infixal, inflectional, inflective,
   lexicographic, lexicological, lexicostatistical, lingual,
   linguistic, metalinguistic, morphemic, morphologic, morphophonemic,
   organic, organismal, paradigmatic, philological, phonemic,
   phonetic, phonological, prefixal, psycholinguistic, semantic,
   structural, substructural, superstructural, syntactic, tectonic,
   textural