The Collaborative International Dictionary of English v.0.48:
Endolymph \En"do*lymph\, n. [Endo- + lymph: cf. F. endolymphe.] (Anat.) The watery fluid contained in the membranous labyrinth of the internal ear. [1913 Webster]WordNet (r) 3.0 (2006):
endolymph n 1: the bodily fluid that fills the membranous labyrinth of the inner ear