tongue-tied

from WordNet (r) 3.0 (2006)

tongue-tied
    adj 1: unable to express yourself clearly or fluently; "felt
           tongue-tied with embarrassment"; "incoherent with grief"
           [syn: {incoherent}, {tongue-tied}]

from The Collaborative International Dictionary of English v.0.48

Tongue-tied \Tongue"-tied`\, a.
   1. Destitute of the power of distinct articulation; having an
      impediment in the speech, esp. when caused by a short
      fraenum.
      [1913 Webster]

   2. Unable to speak freely, from whatever cause.
      [1913 Webster]

            Love, therefore, and tongue-tied simplicity. --Shak.
      [1913 Webster]