o·se·tra also
os·set·ra 
(
ō-s
ĕt
r
ə)
n. Caviar made from the roe of either of two sturgeons, Acipenser gueldenstaedtii or A. persicus of the Caspian and Black Seas, having a yellowish or brownish color and a nutty flavor.
[From Russian osëtr, sturgeon (probably in its genitive form osetra), from Old Russian osetrŭ; akin to Old Prussian esketres.]