o·se·tra also os·set·ra 
(ō-sĕtrə)
(ō-sĕtrə)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.]