polysynthetic

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Of or relating to a language such as Eskimo or Mohawk, characterized by long, morphologically complex words with a large number of affixes that express syntactic relationships and meanings usually expressed as phrases or sentences in other languages.

from The Century Dictionary.

• In philology, compounded of a number and variety of elements beyond the usual norm; exhibiting excessive intricacy of synthetic structure, as by the incorporation of objective and adverbial elements in the verb forms; incapsulated: as, a, polysynthetic word; characterized by such compounds: as, a polysynthetic language: first applied by Du Ponceau to the class of languages spoken by the Indian tribes of America. Also incorporative and (rarely) megasynthetic.
• In mineralogy, compounded of a number of thin lamellæ) in twinning position to each other, or characterized by this kind of structure: as, a polysynthetic twin. See twin.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Characterized by polysynthesis; agglutinative.
• adjective (Min.) repeated twinning, like that of the triclinic feldspar, producing fine parallel bands in alternately reversed positions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective grammar said of a language, characterized by a prevalence of relatively long words containing a large number of morphemes. Typically, the morphemes are bound (i.e., they cannot stand alone as independent words). An example of a polysynthetic language is Ojibwe, where:
• adjective mineralogy Having layers of twin crystals

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective forming derivative or compound words by putting together constituents each of which expresses a single definite meaning