The Collaborative International Dictionary of English v.0.48:

Semiquaver \Sem"i*qua`ver\ (s[e^]m"[i^]*kw[=a]`v[~e]r), n.
   (Mus.)
   A note of half the duration of the quaver; -- now usually
   called a sixteenth note.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sixteenth \Six"teenth`\, a. [From Sixteen: cf. AS.
   sixte['o]?a.]
   1. Sixth after the tenth; next in order after the fifteenth.
      [1913 Webster]

   2. Constituting or being one of sixteen equal parts into
      which anything is divided.
      [1913 Webster]

   Sixteenth note (Mus.), the sixteenth part of a whole note;
      a semiquaver.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sixteenth note
    n 1: a musical note having the time value of a sixteenth of a
         whole note [syn: sixteenth note, semiquaver]