Definition of "decussate"

decussate

/dɪˈkʌseɪt/

adjective
comparative more decussate, superlative most decussate
1. Crossed; intersected; resembling a letter X.
2. (zoology) Having anatomical structures or markings crossing each other, typically in an X shape or at right angles.
3. (botany) Having opposite leaves arranged alternately at right angles.
  Quotations
  Juniperites, ju-ne-per-i′tis, s[ubstantive]. A genus of fossil plants, in which the branches are ranged irregularly; leaves short, obtuse, inserted by a broad base, opposite, decussate, and arranged in four rows.
  1849, John Craig, “Juniperites”, in A New Universal Etymological, Technological, and Pronouncing Dictionary of the English Language, Embracing All the Terms Used in Art, Science, and Literature, volumes II (Jac–Zyt), London: Published (for the proprietors,) by Henry George Collins, 22 Paternoster Row, page 15
4. (rhetoric) Consisting of two rising and two falling clauses, placed in alternate opposition to each other.
verb
third-person singular simple present decussates, present participle decussating, simple past and past participle decussated
1. To form an X or to cross or intersect.
  Quotations
  The two trochlears decussate in the anterior medullary velum.
  1949, Herbert Eugene Walter, Leonard Perkins Sayles, Biology of the Vertebrates