The Collaborative International Dictionary
Equi-
Equi- \E"qui-\ [L. aequus equal. See Equal.] A prefix, meaning equally; as, equidistant; equiangular.
Douglas Harper's Etymology Dictionary
equi-
before vowels equ-, word-forming element meaning "equal, having equal," from Latin aequi-, comb. form of aequus "equal, even" (see equal (adj.)).
Wiktionary
equi-
pre. equal