The Collaborative International Dictionary of English v.0.48:

gluteus \glu*te"us\, glutaeus \glu*t[ae]"us\, n. [NL. See
   Gluteal.] (Anat.)
   Any of several muscles in the buttocks of man and most
   mammals, especially the great muscle of the buttock (the
   gluteus maximus); also, the corresponding muscle in many
   lower animals.
   [1913 Webster +PJC]

   Note: In man, the gluteus is composed of three distinct
         parts, which extend and abduct the thigh, and help
         support the body in standing.
         [1913 Webster]

WordNet (r) 3.0 (2006):

gluteus maximus
    n 1: the outermost of the three gluteal muscles