The Collaborative International Dictionary of English v.0.48:

Inquire \In*quire"\, v. i. [imp. & p. p. Inquired; p. pr. &
   vb. n. Inquiring.] [OE. enqueren, inqueren, OF. enquerre,
   F. enqu['e]rir, L. inquirere, inquisitum; pref. in- in +
   quarere to seek. See Quest a seeking, and cf. Inquiry.]
   [Written also enquire.]
   1. To ask a question; to seek for truth or information by
      putting queries.
      [1913 Webster]

            We will call the damsel, and inquire. --Gen. xxiv.
                                                  57.
      [1913 Webster]

            Then David inquired of the Lord yet again. And the
            Lord answered him.                    --1 Sam.
                                                  xxiii. 4.
      [1913 Webster]

   2. To seek to learn anything by recourse to the proper means
      of knowledge; to make examination.
      [1913 Webster]

            And inquire
            Gladly into the ways of God with man. --Miltom.
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   Note: This word is followed by of before the person asked;
         as, to inquire of a neighbor. It is followed by
         concerning, after, or about, before the subject of
         inquiry; as, his friends inquired about or concerning
         his welfare. "Thou dost not inquire wisely concerning
         this." --Eccl. vii. 10. It is followed by into when
         search is made for particular knowledge or information;
         as, to inquire into the cause of a sudden death. It is
         followed by for or after when a place or person is
         sought, or something is missing. "Inquire in the house
         of Judas for one called Saul of Tarsus." --Acts ix. 11.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Enquire \En*quire"\, v. i. & t.
   See Inquire.
   [1913 Webster]

WordNet (r) 3.0 (2006):

enquire
    v 1: inquire about; "I asked about their special today"; "He had
         to ask directions several times" [syn: ask, inquire,
         enquire]
    2: conduct an inquiry or investigation of; "The district
       attorney's office investigated reports of possible
       irregularities"; "inquire into the disappearance of the rich
       old lady" [syn: investigate, inquire, enquire]
    3: have a wish or desire to know something; "He wondered who had
       built this beautiful church" [syn: wonder, inquire,
       enquire]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "enquire":
   ask, ask a question, ask about, ask questions, be curious,
   bring into question, burn with curiosity, demand, dig around for,
   dig up, gape, gawk, inquire, inquire of, interpellate, interrogate,
   make inquiry, nose around for, nose out, peer, propose a question,
   propound a question, put queries, query, question, quiz,
   require an answer, rubber, rubberneck, seek, stare, want to know