The Collaborative International Dictionary of English v.0.48:

anaphrodisiac \an*aph`ro*dis"i*ac\
   ([a^]n*[a^]f`r[-o]*d[i^]z"[i^]*[a^]k), a. & n. [Gr. 'an priv.
   + 'afrodisiako`s pertaining to venery.] (Med.)
   Same as Antaphrodisiac. --Dunglison. AS
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

antaphrodisiac \ant`aph*ro*dis"i*ac\
   ([a^]nt`[a^]f*r[-o]*d[i^]z"[i^]*[a^]k), anaphrodisiac
\an`aph*ro*dis"i*ac\([a^]n`[a^]f*r[-o]*d[i^]z"[i^]*[a^]k), a.
   [Pref. anti- + aphrodisiac.] (Med.)
   Capable of blunting the sexual appetite. -- n. Anything that
   reduces the sexual appetite.
   [1913 Webster + AS]

WordNet (r) 3.0 (2006):

anaphrodisiac
    adj 1: tending to diminish sexual desire [ant: aphrodisiac,
           aphrodisiacal, sexy]