The Collaborative International Dictionary of English v.0.48:

Interrogate \In*ter"ro*gate\, v. i.
   To ask questions. --Bacon.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Interrogate \In*ter"ro*gate\, n.
   An interrogation; a question. [Obs.] --Bp. Hall.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Interrogate \In*ter"ro*gate\, v. t. [imp. & p. p.
   Interrogating.] [L. interrogatus, p. p. of interrogare to
   ask; inter between + rogare to ask. See Rogation.]
   To question formally; to question; to examine by asking
   questions; as, to interrogate a witness.
   [1913 Webster]

         Wilt thou, uncalled, interrogate,
         Talker! the unreplying Fate?             --Emerson.

   Syn: To question; ask. See Question.
        [1913 Webster]

WordNet (r) 3.0 (2006):

interrogate
    v 1: transmit (a signal) for setting off an appropriate
         response, as in telecommunication
    2: pose a series of questions to; "The suspect was questioned by
       the police"; "We questioned the survivor about the details of
       the explosion" [syn: interrogate, question]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "interrogate":
   answer, approach, ask, be curious, burn with curiosity, catechize,
   communicate with, contact, correspond, dig around for, dig up,
   establish connection, examine, gape, gawk, get to, inquire,
   interview, maintain connection, make advances, make contact with,
   make overtures, make up to, nose around for, nose out, peer, pump,
   query, question, quiz, raise, reach, relate to, reply to,
   respond to, rubber, rubberneck, seek, stare, test, want to know,
   worm out of