The Collaborative International Dictionary
Ypsiliform
Ypsiliform \Yp*sil"i*form\, a. [Gr. ? ? the name of the letter ? + -form.] (Biol.) Resembling the ? in appearance; -- said of the germinal spot in the ripe egg at one of the stages of fecundation.
Wiktionary
ypsiliform
a. in the shape of an ypsilon