массовый [mássovȳĭ] (m) = mass (adj), popular, bulk (adj)

На северо-востоке Словении нашли массовое захоронение.

na severovostóke slovénii nashlí mássovoe zakhoronénie.

= A mass grave was found in the northeast of Slovenia.

https://www.learnwitholiver.com/russian/daily-sentence-2293