seminal vesicle

https://doi.org/10.1351/goldbook.11203

One of a pair of glands of the male reproductive system that together produce a significant portion of the semen.

Note: Seminal vesicle secretion does not contain spermatozoa, but provides nutrients and an alkaline environment that prolongs their survival.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 803 (https://doi.org/10.1515/pac-2015-1202)