The Collaborative International Dictionary of English v.0.48:

Halacha \Ha*la"cha\ (h[.a]*l[aum]"k[.a]), n.; pl. Halachoth
   (-k[=o]th). [Heb. hal[=a]ch[=a]h.]
   The general term for the Hebrew oral or traditional law; one
   of two branches of exposition in the Midrash. See Midrash.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Halacha
    n 1: Talmudic literature that deals with law and with the
         interpretation of the laws on the Hebrew Scriptures [syn:
         Halakah, Halaka, Halacha]