The Collaborative International Dictionary of English v.0.48:

Dilate \Di*late"\ (?; 277), v. t. [imp. & p. p. Dilated; p.
   pr. & vb. n. Dilating.] [L. dilatare; either fr. di- = dis-
   + latus wide, not the same word as latus, used as p. p. of
   ferre to bear (see Latitude); or fr. dilatus, used as p. p.
   of differre to separate (see Delay, Tolerate, Differ,
   and cf. Dilatory): cf. F. dilater.]
   1. To expand; to distend; to enlarge or extend in all
      directions; to swell; -- opposed to contract; as, the
      air dilates the lungs; air is dilated by increase of heat.
      [1913 Webster]

   2. To enlarge upon; to relate at large; to tell copiously or
      diffusely. [R.]
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            Do me the favor to dilate at full
            What hath befallen of them and thee till now.
                                                  --Shak.

   Syn: To expand; swell; distend; enlarge; spread out; amplify;
        expatiate.
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The Collaborative International Dictionary of English v.0.48:

Dilate \Di*late"\, v. i.
   1. To grow wide; to expand; to swell or extend in all
      directions.
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            His heart dilates and glories in his strength.
                                                  --Addison.
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   2. To speak largely and copiously; to dwell in narration; to
      enlarge; -- with on or upon.
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            But still on their ancient joys dilate. --Crabbe.
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The Collaborative International Dictionary of English v.0.48:

Dilate \Di*late"\, a.
   Extensive; expanded. [Obs.] --B. Jonson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dilate
    v 1: become wider; "His pupils were dilated" [syn: dilate,
         distend]
    2: add details, as to an account or idea; clarify the meaning of
       and discourse in a learned way, usually in writing; "She
       elaborated on the main ideas in her dissertation" [syn:
       elaborate, lucubrate, expatiate, exposit, enlarge,
       flesh out, expand, expound, dilate] [ant:
       abbreviate, abridge, contract, cut, foreshorten,
       reduce, shorten]