Source : Webster's Revised Unabridged Dictionary (1913)

Imperforate \Im*per"fo*rate\, Imperforated \Im*per"fo*ra"ted\,
   a. [L. pref. im- not + perforatus, p. p. of perforate to
   perforate. See {Perforate}.]
   Not perforated; having no opening or aperture. --Sir J.
   Banks.

Source : WordNet®

imperforate
     adj : not perforated; having no opening